feat(notify): bundled notifications, task watchers, daily summary

- Per-user routing (own mail / own Discord webhook) for task alarms
  (sent at once), shares, completed shared tasks and watched tasks;
  settings as JSON on the user (GET /auth/me, PATCH /auth/settings).
- Everything but alarms is queued and sent as one message per user
  after NOTIFY_DIGEST_MINUTES (default 5); mails now multipart with an
  HTML version, Discord as one embed. Three failed attempts drop it.
- Own changes never notify the actor, except on watched tasks when
  asked for; "paused" stops everything including alarms.
- Task watchers: POST/DELETE /tasks/{id}/watch, isWatching on tasks.
- Daily summary at a chosen time: overdue, today, tomorrow, plus the
  count of the next 7 days; nothing due, nothing sent.
- Migration 7; jobs do not run in the demo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/alarms.go

@@ -13,6 +13,11 @@ import (
 // --- MULTI-CHANNEL ALARM DISPATCHER (EMAIL, DISCORD, CUSTOM WEBHOOK) ---
 
 func (s *Server) sendEmailNotification(toEmail, subject, bodyText string) error {
+	return s.sendEmailHTML(toEmail, subject, bodyText, "")
+}
+
+// sendEmailHTML sends text plus an optional HTML version (multipart/alternative).
+func (s *Server) sendEmailHTML(toEmail, subject, bodyText, html string) error {
 	if s.cfg.DemoMode {
 		return errDemoOutgoing
 	}
@@ -20,7 +25,7 @@ func (s *Server) sendEmailNotification(toEmail, subject, bodyText string) error
 	if err != nil {
 		return err
 	}
-	if err := sendMail(cfg, toEmail, subject, bodyText); err != nil {
+	if err := sendMail(cfg, toEmail, subject, bodyText, html); err != nil {
 		step := ""
 		if se, ok := err.(*smtpStepError); ok {
 			step = se.Step
@@ -123,6 +128,27 @@ func (s *Server) startAlarmTicker() {
 			if !alarmDue(a.DueDate, a.NotifyBeforeMinutes, now) {
 				continue
 			}
+			// Channels come from the notification settings (row "due"); a pause holds the alarm back
+			set := s.store.NotificationSettingsOf(a.UserID)
+			if set.Paused {
+				continue
+			}
+			channels := []string{}
+			if set.Events.Due.Email {
+				channels = append(channels, "email")
+			}
+			if set.Events.Due.Discord {
+				channels = append(channels, "discord")
+			}
+			for _, ch := range a.AlarmChannels {
+				if ch == "webhook" {
+					channels = append(channels, "webhook")
+				}
+			}
+			if a.AlarmEmail == "" {
+				a.AlarmEmail = a.UserEmail
+			}
+			a.AlarmChannels = channels
 			if len(a.AlarmChannels) == 0 {
 				continue
 			}

internal/api/handlers_auth.go

@@ -341,6 +341,8 @@ func (s *Server) handleMe(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	stats, _ := s.store.GetDashboardStats(userID)
+	ns := s.store.NotificationSettingsOf(userID)
+	user.NotificationSettings = &ns
 	writeJSON(w, http.StatusOK, map[string]interface{}{
 		"user":  user,
 		"stats": stats,
@@ -448,6 +450,8 @@ func (s *Server) handleUpdateUserSettings(w http.ResponseWriter, r *http.Request
 		NotifyBeforeMinutes *int      `json:"notifyBeforeMinutes"`
 		// Needed to change password or e-mail address (FLAW-30)
 		CurrentPassword string `json:"currentPassword"`
+		// Which notifications go where (notify.go)
+		NotificationSettings *domain.NotificationSettings `json:"notificationSettings"`
 	}
 	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
 		writeError(w, http.StatusBadRequest, "Ungültiges JSON")
@@ -528,6 +532,14 @@ func (s *Server) handleUpdateUserSettings(w http.ResponseWriter, r *http.Request
 	if changesPassword || changesEmail {
 		s.notifyAccountChange(before, changesPassword, changesEmail, u.Email)
 	}
+	if req.NotificationSettings != nil {
+		if err := s.store.SetNotificationSettings(userID, *req.NotificationSettings); err != nil {
+			writeError(w, http.StatusInternalServerError, "Benachrichtigungen konnten nicht gespeichert werden")
+			return
+		}
+	}
+	ns := s.store.NotificationSettingsOf(userID)
+	u.NotificationSettings = &ns
 	writeJSON(w, http.StatusOK, u)
 }
 

internal/api/handlers_documents.go

@@ -262,6 +262,9 @@ func (s *Server) handleCreateDocShare(w http.ResponseWriter, r *http.Request) {
 
 	if req.TeamID != "" {
 		share, err := s.store.CreateDocTeamShare(userID, docID, req.TeamID, req.Permission)
+		if err == nil {
+			defer s.notifyShared(userID, "team", req.TeamID, "die Notiz", s.docTitle(userID, docID))
+		}
 		if err != nil {
 			writeError(w, http.StatusBadRequest, err.Error())
 			return
@@ -286,6 +289,7 @@ func (s *Server) handleCreateDocShare(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, err.Error())
 		return
 	}
+	s.notifyShared(userID, "user", share.UserID, "die Notiz", s.docTitle(userID, docID))
 	s.broadcastDocToAuthorizedUsers(docID, "DOC_CREATED")
 	s.broadcastDocToAuthorizedUsers(docID, "DOC_UPDATED")
 	writeJSON(w, http.StatusCreated, share)
@@ -313,3 +317,10 @@ func (s *Server) handleGetCollaborators(w http.ResponseWriter, r *http.Request)
 	}
 	writeJSON(w, http.StatusOK, users)
 }
+
+func (s *Server) docTitle(userID, docID string) string {
+	if d, err := s.store.GetDocumentByID(userID, docID); err == nil && d.Title != "" {
+		return d.Title
+	}
+	return "Unbenannte Notiz"
+}

internal/api/handlers_folders.go

@@ -212,6 +212,7 @@ func (s *Server) handleCreateFolderShare(w http.ResponseWriter, r *http.Request)
 		writeError(w, http.StatusBadRequest, err.Error())
 		return
 	}
+	s.notifyShared(userID, share.TargetType, share.TargetID, "den Ordner", s.store.SharedFolderName(folderID))
 	s.wsHub.BroadcastToUsers(s.store.GetSharedFolderUserIDs(folderID), "WORKSPACE_FOLDERS_UPDATED", map[string]string{"folderId": folderID})
 	if docIDs, err := s.store.GetSharedFolderDocIDs(folderID); err == nil {
 		for _, docID := range docIDs {

internal/api/handlers_lists.go

@@ -107,6 +107,9 @@ func (s *Server) handleCreateListShare(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if l, err := s.store.GetListByID(currentUserID, listID); err == nil {
+		s.notifyShared(currentUserID, targetType, share.TargetID, "die Liste", l.Title)
+	}
 	if targetType == "team" {
 		members, _ := s.store.GetTeamMembers(share.TargetID)
 		for _, tm := range members {

internal/api/handlers_tasklists.go

@@ -125,6 +125,9 @@ func (s *Server) handleCreateTaskListShare(w http.ResponseWriter, r *http.Reques
 		return
 	}
 	s.broadcastTaskListChange(listID, nil, "TASK_LIST_UPDATED")
+	if tl, err := s.store.GetTaskListByID(userID, listID); err == nil {
+		s.notifyShared(userID, req.TargetType, req.TargetID, "die Aufgabenliste", tl.Title)
+	}
 	writeJSON(w, http.StatusCreated, share)
 }
 

internal/api/handlers_thoughts.go

@@ -94,6 +94,7 @@ func (s *Server) handleGetThoughts(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusInternalServerError, err.Error())
 		return
 	}
+	s.markWatching(userID, thoughts)
 	writeJSON(w, http.StatusOK, thoughts)
 }
 
@@ -278,6 +279,8 @@ func (s *Server) handleUpdateThought(w http.ResponseWriter, r *http.Request) {
 		s.notifyDocChanged(docID, head)
 	}
 	s.wsHub.BroadcastToUsers(append(s.taskAudience(before), s.taskAudience(updated)...), "TASK_UPDATED", updated)
+	s.notifyTaskChange(userID, before, updated, false)
+	updated.IsWatching = s.store.WatchedTaskIDs(userID)[updated.ID]
 	writeJSON(w, http.StatusOK, updated)
 }
 
@@ -304,6 +307,9 @@ func (s *Server) handleDeleteThought(w http.ResponseWriter, r *http.Request) {
 		writeStoreError(w, http.StatusInternalServerError, err)
 		return
 	}
+	if th != nil {
+		s.notifyTaskChange(userID, th, nil, true)
+	}
 	s.wsHub.BroadcastToUsers(audience, "TASK_DELETED", map[string]string{"id": thoughtID})
 	writeJSON(w, http.StatusOK, map[string]bool{"deleted": true})
 }

internal/api/mail.go

@@ -117,7 +117,7 @@ func senderAddress(raw, name string) (envelope, header string, err error) {
 
 // buildMessage creates an RFC 5322 message: Date and Message-ID headers, RFC 2047 encoded subject
 // (umlauts, emoji) and a quoted-printable UTF-8 body with CRLF line endings.
-func buildMessage(from, to, subject, body string, now time.Time) []byte {
+func buildMessage(from, to, subject, body, html string, now time.Time) []byte {
 	idBytes := make([]byte, 12)
 	_, _ = rand.Read(idBytes)
 	domain := ehloName(from)
@@ -129,12 +129,26 @@ func buildMessage(from, to, subject, body string, now time.Time) []byte {
 	fmt.Fprintf(&buf, "Date: %s\r\n", now.Format(time.RFC1123Z))
 	fmt.Fprintf(&buf, "Message-ID: <%s@%s>\r\n", hex.EncodeToString(idBytes), domain)
 	buf.WriteString("MIME-Version: 1.0\r\n")
-	buf.WriteString("Content-Type: text/plain; charset=\"utf-8\"\r\n")
-	buf.WriteString("Content-Transfer-Encoding: quoted-printable\r\n\r\n")
-	qp := quotedprintable.NewWriter(&buf)
-	_, _ = qp.Write([]byte(strings.ReplaceAll(strings.ReplaceAll(body, "\r\n", "\n"), "\n", "\r\n")))
-	_ = qp.Close()
-	buf.WriteString("\r\n")
+	part := func(contentType, text string) {
+		fmt.Fprintf(&buf, "Content-Type: %s; charset=\"utf-8\"\r\n", contentType)
+		buf.WriteString("Content-Transfer-Encoding: quoted-printable\r\n\r\n")
+		qp := quotedprintable.NewWriter(&buf)
+		_, _ = qp.Write([]byte(strings.ReplaceAll(strings.ReplaceAll(text, "\r\n", "\n"), "\n", "\r\n")))
+		_ = qp.Close()
+		buf.WriteString("\r\n")
+	}
+	if html == "" {
+		part("text/plain", body)
+		return buf.Bytes()
+	}
+	// Text for simple clients, HTML for the rest
+	boundary := "ms-" + hex.EncodeToString(idBytes)
+	fmt.Fprintf(&buf, "Content-Type: multipart/alternative; boundary=\"%s\"\r\n\r\n", boundary)
+	fmt.Fprintf(&buf, "--%s\r\n", boundary)
+	part("text/plain", body)
+	fmt.Fprintf(&buf, "--%s\r\n", boundary)
+	part("text/html", html)
+	fmt.Fprintf(&buf, "--%s--\r\n", boundary)
 	return buf.Bytes()
 }
 
@@ -199,14 +213,14 @@ func authenticate(client *smtp.Client, cfg smtpSettings) error {
 
 // sendMail sends one mail. If AUTH PLAIN is refused and the server also offers LOGIN, it reconnects once
 // and tries LOGIN; a 451 on both points to the mail server's SASL backend.
-func sendMail(cfg smtpSettings, to, subject, body string) error {
-	err := sendMailOnce(cfg, to, subject, body)
+func sendMail(cfg smtpSettings, to, subject, body, html string) error {
+	err := sendMailOnce(cfg, to, subject, body, html)
 	var first *authAttemptError
 	if cfg.authMech != "" || !errors.As(err, &first) || first.mech != "PLAIN" || !first.loginOffered {
 		return err
 	}
 	cfg.authMech = "LOGIN"
-	retryErr := sendMailOnce(cfg, to, subject, body)
+	retryErr := sendMailOnce(cfg, to, subject, body, html)
 	var second *authAttemptError
 	if retryErr == nil || !errors.As(retryErr, &second) {
 		return retryErr
@@ -220,7 +234,7 @@ func sendMail(cfg smtpSettings, to, subject, body string) error {
 
 // sendMailOnce runs the SMTP dialogue step by step instead of smtp.SendMail, so it can introduce itself
 // properly, honour SkipVerify and report the exact step a server refuses.
-func sendMailOnce(cfg smtpSettings, to, subject, body string) error {
+func sendMailOnce(cfg smtpSettings, to, subject, body, html string) error {
 	fromAddr, fromHeader, err := senderAddress(cfg.From, cfg.FromName)
 	if err != nil {
 		return &smtpStepError{"Absender", err}
@@ -278,7 +292,7 @@ func sendMailOnce(cfg smtpSettings, to, subject, body string) error {
 	if err != nil {
 		return &smtpStepError{"DATA", err}
 	}
-	if _, err := wc.Write(buildMessage(fromHeader, toHeader, subject, body, time.Now())); err != nil {
+	if _, err := wc.Write(buildMessage(fromHeader, toHeader, subject, body, html, time.Now())); err != nil {
 		_ = wc.Close()
 		return &smtpStepError{"DATA", err}
 	}

internal/api/mail_test.go

@@ -175,13 +175,13 @@ func TestSendMailStartTLSWithSelfSignedCertificate(t *testing.T) {
 	f := startFakeSMTP(t, "")
 
 	// The certificate is self-signed: refused unless verification is switched off
-	err := sendMail(f.settings(false), "anna@example.com", "Test", "Hallo")
+	err := sendMail(f.settings(false), "anna@example.com", "Test", "Hallo", "")
 	var stepErr *smtpStepError
 	if !errors.As(err, &stepErr) || stepErr.Step != "STARTTLS" {
 		t.Fatalf("expected a STARTTLS error with verification on, got %v", err)
 	}
 
-	if err := sendMail(f.settings(true), "anna@example.com", "⏰ Aufgabe fällig: Müll", "Zeile 1\nZeile 2 mit Ümlaut"); err != nil {
+	if err := sendMail(f.settings(true), "anna@example.com", "⏰ Aufgabe fällig: Müll", "Zeile 1\nZeile 2 mit Ümlaut", ""); err != nil {
 		t.Fatalf("send with SkipVerify failed: %v", err)
 	}
 	f.mu.Lock()
@@ -206,7 +206,7 @@ func TestSendMailStartTLSWithSelfSignedCertificate(t *testing.T) {
 
 func TestSendMailReportsTheRefusingStep(t *testing.T) {
 	f := startFakeSMTP(t, "451 4.3.2 Internal server error")
-	err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo")
+	err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo", "")
 	var stepErr *smtpStepError
 	if !errors.As(err, &stepErr) || stepErr.Step != "RCPT TO" || !strings.Contains(err.Error(), "451") {
 		t.Fatalf("expected the 451 to be reported at RCPT TO, got %v", err)
@@ -218,7 +218,7 @@ func TestSendMailWithDisplayNameSender(t *testing.T) {
 	f := startFakeSMTP(t, "")
 	cfg := f.settings(true)
 	cfg.From = "MindSift Alarme <alarm@firma.de>"
-	if err := sendMail(cfg, "Anna <anna@example.com>", "Test", "Hallo"); err != nil {
+	if err := sendMail(cfg, "Anna <anna@example.com>", "Test", "Hallo", ""); err != nil {
 		t.Fatalf("send failed: %v", err)
 	}
 	f.mu.Lock()
@@ -244,7 +244,7 @@ func TestAuthFallsBackToLogin(t *testing.T) {
 	f := startFakeSMTP(t, "")
 	f.authMechs = "PLAIN LOGIN"
 	f.authFail["PLAIN"] = "451 4.3.2 Internal server error"
-	if err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo"); err != nil {
+	if err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo", ""); err != nil {
 		t.Fatalf("LOGIN fallback should succeed: %v", err)
 	}
 	f.mu.Lock()
@@ -257,7 +257,7 @@ func TestAuthFallsBackToLogin(t *testing.T) {
 func TestAuthLoginOnlyAndBothFailing(t *testing.T) {
 	f := startFakeSMTP(t, "")
 	f.authMechs = "LOGIN"
-	if err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo"); err != nil {
+	if err := sendMail(f.settings(true), "anna@example.com", "Test", "Hallo", ""); err != nil {
 		t.Fatalf("LOGIN-only server: %v", err)
 	}
 
@@ -265,7 +265,7 @@ func TestAuthLoginOnlyAndBothFailing(t *testing.T) {
 	g.authMechs = "PLAIN LOGIN"
 	g.authFail["PLAIN"] = "451 4.3.2 Internal server error"
 	g.authFail["LOGIN"] = "451 4.3.2 Internal server error"
-	err := sendMail(g.settings(true), "anna@example.com", "Test", "Hallo")
+	err := sendMail(g.settings(true), "anna@example.com", "Test", "Hallo", "")
 	if err == nil || !strings.Contains(err.Error(), "PLAIN") || !strings.Contains(err.Error(), "LOGIN") || !strings.Contains(err.Error(), "SASL") {
 		t.Fatalf("expected both mechanisms and the server hint in the error, got %v", err)
 	}

internal/api/notify.go

@@ -0,0 +1,417 @@
+package api
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"html"
+	"log/slog"
+	"net/http"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/sandrodach/mindsift/internal/auth"
+	"github.com/sandrodach/mindsift/internal/domain"
+)
+
+// Notifications besides task alarms: events go into a queue per recipient and are sent bundled, one
+// message per recipient and channel once the oldest event is NOTIFY_DIGEST_MINUTES old. Each user picks
+// the channels per event kind (own mail address, own Discord webhook from the alarm settings), can
+// pause everything and gets a daily summary of due tasks at a chosen time. Own changes never notify the
+// one who made them, except on watched tasks when the user asked for it. The demo sends nothing.
+
+const notifyMaxAttempts = 3
+
+// notifyItem is one line of a bundled message.
+type notifyItem struct {
+	kind, title, text string
+}
+
+// notify queues an event for the recipients that want it (settings, pause, own-change rule).
+func (s *Server) notify(kind, actorID string, recipients []string, payload map[string]string) {
+	if s.cfg.DemoMode {
+		return
+	}
+	seen := map[string]bool{}
+	for _, uid := range recipients {
+		if uid == "" || seen[uid] {
+			continue
+		}
+		seen[uid] = true
+		set := s.store.NotificationSettingsOf(uid)
+		if set.Paused {
+			continue
+		}
+		if uid == actorID && !(kind == "watched" && set.IncludeOwnWatched) {
+			continue
+		}
+		if ch := set.Channels(kind); !ch.Email && !ch.Discord {
+			continue
+		}
+		if err := s.store.QueueNotification(uid, kind, payload); err != nil {
+			slog.Warn("Benachrichtigung konnte nicht vorgemerkt werden", "user_id", uid, "error", err)
+		}
+	}
+}
+
+func (s *Server) actorName(userID string) string {
+	if u, err := s.store.GetUserByID(userID); err == nil && u != nil && u.DisplayName != "" {
+		return u.DisplayName
+	}
+	return "Jemand"
+}
+
+// notifyShared tells the people a note, folder or list was shared with (teams: all members).
+func (s *Server) notifyShared(actorID, targetType, targetID, what, title string) {
+	var recipients []string
+	if targetType == "team" {
+		members, _ := s.store.GetTeamMembers(targetID)
+		for _, m := range members {
+			recipients = append(recipients, m.UserID)
+		}
+	} else {
+		recipients = []string{targetID}
+	}
+	s.notify("shared", actorID, recipients, map[string]string{
+		"title": title,
+		"text":  fmt.Sprintf("%s hat %s „%s“ mit dir geteilt", s.actorName(actorID), what, title),
+	})
+}
+
+// notifyTaskChange covers watchers (any change) and list members (task completed).
+func (s *Server) notifyTaskChange(actorID string, before, after *domain.Thought, deleted bool) {
+	t := after
+	if t == nil {
+		t = before
+	}
+	if t == nil {
+		return
+	}
+	title := strings.TrimSpace(strings.SplitN(t.Content, "\n", 2)[0])
+	name := s.actorName(actorID)
+	var change string
+	switch {
+	case deleted:
+		change = "gelöscht"
+	case before != nil && after != nil && !before.IsCompleted && after.IsCompleted:
+		change = "erledigt"
+	case before != nil && after != nil && before.IsCompleted && !after.IsCompleted:
+		change = "wieder geöffnet"
+	case before != nil && after != nil && before.DueDate != after.DueDate:
+		change = "Fälligkeit geändert auf " + domain.HumanDue(after.DueDate)
+	case before != nil && after != nil && before.Content != after.Content:
+		change = "Text geändert"
+	case before != nil && after != nil && before.Priority != after.Priority:
+		change = "Priorität geändert auf " + after.Priority
+	case before != nil && after != nil && before.TaskListID != after.TaskListID:
+		change = "in eine andere Liste verschoben"
+	default:
+		change = "geändert"
+	}
+	payload := map[string]string{"title": title, "text": fmt.Sprintf("%s hat „%s“ %s", name, title, change)}
+	watchers := s.store.TaskWatchers(t.ID)
+	s.notify("watched", actorID, watchers, payload)
+
+	if change == "erledigt" && t.TaskListID != "" {
+		watching := map[string]bool{}
+		for _, w := range watchers {
+			watching[w] = true
+		}
+		var members []string
+		for _, uid := range s.taskAudience(t) {
+			if !watching[uid] { // watchers already hear about it
+				members = append(members, uid)
+			}
+		}
+		s.notify("taskDone", actorID, members, payload)
+	}
+	if deleted {
+		s.store.ForgetTaskWatchers(t.ID)
+	}
+}
+
+// --- Background jobs ---
+
+func (s *Server) startNotificationJobs() {
+	ticker := time.NewTicker(time.Minute)
+	defer ticker.Stop()
+	for now := range ticker.C {
+		s.flushNotifications(now)
+		s.sendDailySummaries(now)
+	}
+}
+
+// flushNotifications sends one bundled message per recipient whose oldest event waited long enough.
+func (s *Server) flushNotifications(now time.Time) {
+	minutes := s.cfg.NotifyDigestMinutes
+	if minutes < 1 {
+		minutes = 5
+	}
+	window := time.Duration(minutes) * time.Minute
+	users, err := s.store.DueNotificationUsers(now.Add(-window))
+	if err != nil {
+		slog.Error("Benachrichtigungen konnten nicht gelesen werden", "error", err)
+		return
+	}
+	for _, uid := range users {
+		queued, err := s.store.QueuedNotifications(uid)
+		if err != nil || len(queued) == 0 {
+			continue
+		}
+		set := s.store.NotificationSettingsOf(uid)
+		var emailItems, discordItems []notifyItem
+		ids := make([]int64, 0, len(queued))
+		maxAttempts := 0
+		for _, q := range queued {
+			ids = append(ids, q.ID)
+			if q.Attempts > maxAttempts {
+				maxAttempts = q.Attempts
+			}
+			if set.Paused {
+				continue
+			}
+			item := notifyItem{kind: q.Kind, title: q.Payload["title"], text: q.Payload["text"]}
+			ch := set.Channels(q.Kind)
+			if ch.Email {
+				emailItems = append(emailItems, item)
+			}
+			if ch.Discord {
+				discordItems = append(discordItems, item)
+			}
+		}
+		if err := s.deliver(uid, "Neuigkeiten", emailItems, discordItems); err != nil {
+			if maxAttempts+1 >= notifyMaxAttempts {
+				slog.Warn("Benachrichtigungen nach mehreren Fehlversuchen verworfen", "user_id", uid, "count", len(ids), "error", err)
+				_ = s.store.DeleteQueuedNotifications(ids)
+			} else {
+				_ = s.store.BumpQueuedNotifications(ids)
+			}
+			continue
+		}
+		_ = s.store.DeleteQueuedNotifications(ids)
+	}
+}
+
+// deliver sends the items to the user's mail address and/or Discord webhook.
+func (s *Server) deliver(userID, heading string, emailItems, discordItems []notifyItem) error {
+	u, err := s.store.GetUserByID(userID)
+	if err != nil || u == nil || !u.IsActive {
+		return nil // account gone: nothing to deliver
+	}
+	var firstErr error
+	if len(emailItems) > 0 {
+		to := u.AlarmEmail
+		if to == "" {
+			to = u.Email
+		}
+		subject := "MindSift: " + heading
+		if len(emailItems) == 1 {
+			subject = "MindSift: " + emailItems[0].text
+		}
+		if err := s.sendNotifyEmail(to, subject, notifyText(heading, emailItems, s.notifyLink()), notifyHTML(heading, emailItems, s.notifyLink())); err != nil {
+			firstErr = err
+		}
+	}
+	if len(discordItems) > 0 && u.DiscordWebhookURL != "" {
+		if err := s.sendNotifyDiscord(u.DiscordWebhookURL, heading, discordItems); err != nil && firstErr == nil {
+			firstErr = err
+		}
+	}
+	return firstErr
+}
+
+// sendNotifyEmail / sendNotifyDiscord are replaced in tests.
+func (s *Server) sendNotifyEmail(to, subject, text, htmlBody string) error {
+	if s.notifyEmailHook != nil {
+		return s.notifyEmailHook(to, subject, text, htmlBody)
+	}
+	return s.sendEmailHTML(to, subject, text, htmlBody)
+}
+
+func (s *Server) sendNotifyDiscord(webhookURL, heading string, items []notifyItem) error {
+	if s.notifyDiscordHook != nil {
+		return s.notifyDiscordHook(webhookURL, heading, items)
+	}
+	return s.sendDiscordDigest(webhookURL, heading, items)
+}
+
+func (s *Server) notifyLink() string {
+	if !s.cfg.BaseURLSet {
+		return ""
+	}
+	return strings.TrimRight(s.cfg.BaseURL, "/") + "/"
+}
+
+// sendDiscordDigest posts one embed with a line per item (at most 10).
+func (s *Server) sendDiscordDigest(webhookURL, heading string, items []notifyItem) error {
+	if s.cfg.DemoMode {
+		return errDemoOutgoing
+	}
+	allowPrivate := s.allowPrivateWebhooks()
+	if err := validateWebhookURL(webhookURL, true, allowPrivate); err != nil {
+		return err
+	}
+	lines := make([]string, 0, 11)
+	for i, it := range items {
+		if i == 10 {
+			lines = append(lines, fmt.Sprintf("… und %d weitere", len(items)-10))
+			break
+		}
+		lines = append(lines, "• "+it.text)
+	}
+	body, _ := json.Marshal(map[string]interface{}{
+		"embeds": []map[string]interface{}{{
+			"title":       "MindSift: " + heading,
+			"description": strings.Join(lines, "\n"),
+			"color":       2450411,
+		}},
+	})
+	resp, err := guardedClient(allowPrivate).Post(webhookURL, "application/json", bytes.NewReader(body))
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 400 {
+		return fmt.Errorf("HTTP Status %d", resp.StatusCode)
+	}
+	return nil
+}
+
+func notifyText(heading string, items []notifyItem, link string) string {
+	var b strings.Builder
+	b.WriteString(heading + "\n\n")
+	for _, it := range items {
+		b.WriteString("• " + it.text + "\n")
+	}
+	if link != "" {
+		b.WriteString("\nÖffnen: " + link + "\n")
+	}
+	b.WriteString("\nDiese Benachrichtigungen stellst du in MindSift unter Kontoeinstellungen → Alarme ein.\n")
+	return b.String()
+}
+
+// notifyHTML: simple table layout with inline styles, no external resources (works in most clients).
+func notifyHTML(heading string, items []notifyItem, link string) string {
+	var cards strings.Builder
+	for _, it := range items {
+		cards.WriteString(`<tr><td style="padding:12px 16px;border:1px solid #e3e6ea;border-radius:8px;background:#ffffff;font-size:14px;color:#1f2328">` +
+			html.EscapeString(it.text) + `</td></tr><tr><td style="height:8px"></td></tr>`)
+	}
+	button := ""
+	if link != "" {
+		button = `<tr><td style="padding-top:8px"><a href="` + html.EscapeString(link) +
+			`" style="display:inline-block;padding:10px 18px;background:#2563eb;color:#ffffff;text-decoration:none;border-radius:6px;font-size:14px">In MindSift öffnen</a></td></tr>`
+	}
+	return `<!doctype html><html><body style="margin:0;padding:24px;background:#f4f5f7;font-family:-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif">` +
+		`<table role="presentation" width="100%" cellpadding="0" cellspacing="0" style="max-width:560px;margin:0 auto">` +
+		`<tr><td style="font-size:18px;font-weight:bold;color:#2563eb;padding-bottom:4px">MindSift</td></tr>` +
+		`<tr><td style="font-size:15px;color:#1f2328;padding-bottom:16px">` + html.EscapeString(heading) + `</td></tr>` +
+		cards.String() + button +
+		`<tr><td style="font-size:12px;color:#6b7280;padding-top:20px">Diese Benachrichtigungen stellst du in MindSift unter Kontoeinstellungen → Alarme ein.</td></tr>` +
+		`</table></body></html>`
+}
+
+// --- Daily summary ---
+
+// sendDailySummaries sends each user who wants one their summary in the 30 minutes after the chosen
+// time, once a day. Nothing due → no message.
+func (s *Server) sendDailySummaries(now time.Time) {
+	day := now.Format("2006-01-02")
+	for _, uid := range s.store.ActiveUserIDs() {
+		set := s.store.NotificationSettingsOf(uid)
+		ds := set.DailySummary
+		if set.Paused || !ds.Enabled || (!ds.Email && !ds.Discord) {
+			continue
+		}
+		at, err := time.ParseInLocation("2006-01-02 15:04", day+" "+ds.Time, now.Location())
+		if err != nil || now.Before(at) || now.Sub(at) >= 30*time.Minute {
+			continue
+		}
+		items := s.summaryItems(uid, now)
+		if len(items) == 0 || !s.store.ClaimDailySummary(uid, day) {
+			continue
+		}
+		var mail, discord []notifyItem
+		if ds.Email {
+			mail = items
+		}
+		if ds.Discord {
+			discord = items
+		}
+		if err := s.deliver(uid, "Deine Aufgaben für heute", mail, discord); err != nil {
+			slog.Warn("Tageszusammenfassung konnte nicht verschickt werden", "user_id", uid, "error", err)
+		}
+	}
+}
+
+// summaryItems: overdue, today, tomorrow (with time), plus how many follow in the next 7 days.
+func (s *Server) summaryItems(userID string, now time.Time) []notifyItem {
+	today := now.Format("2006-01-02")
+	tomorrow := now.AddDate(0, 0, 1).Format("2006-01-02")
+	tasks, err := s.store.OpenTasksDueBefore(userID, now.AddDate(0, 0, 8).Format("2006-01-02"))
+	if err != nil {
+		return nil
+	}
+	sort.SliceStable(tasks, func(i, j int) bool { return tasks[i].DueDate < tasks[j].DueDate })
+	var items []notifyItem
+	later := 0
+	for _, t := range tasks {
+		d := t.DueDate
+		if len(d) > 10 {
+			d = d[:10]
+		}
+		label := t.Title
+		if t.ListTitle != "" {
+			label += " (" + t.ListTitle + ")"
+		}
+		clock := ""
+		if len(t.DueDate) >= 16 {
+			clock = ", " + t.DueDate[11:16] + " Uhr"
+		}
+		switch {
+		case d < today:
+			items = append(items, notifyItem{kind: "due", title: t.Title, text: "Überfällig seit " + domain.HumanDue(t.DueDate) + ": " + label})
+		case d == today:
+			items = append(items, notifyItem{kind: "due", title: t.Title, text: "Heute" + clock + ": " + label})
+		case d == tomorrow:
+			items = append(items, notifyItem{kind: "due", title: t.Title, text: "Morgen" + clock + ": " + label})
+		default:
+			later++
+		}
+	}
+	if len(items) > 0 && later > 0 {
+		items = append(items, notifyItem{kind: "due", text: fmt.Sprintf("Außerdem %d weitere Aufgaben in den nächsten 7 Tagen", later)})
+	}
+	return items
+}
+
+// --- Watching tasks ---
+
+// handleWatchTask: POST (watch) / DELETE (stop) /tasks/{id}/watch
+func (s *Server) handleWatchTask(w http.ResponseWriter, r *http.Request) {
+	userID := auth.GetUserID(r.Context())
+	taskID := chi.URLParam(r, "id")
+	if _, err := s.store.GetThoughtByID(userID, taskID); err != nil {
+		writeError(w, http.StatusNotFound, "Aufgabe nicht gefunden")
+		return
+	}
+	on := r.Method == http.MethodPost
+	if err := s.store.WatchTask(taskID, userID, on); err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]bool{"watching": on})
+}
+
+// markWatching sets IsWatching on tasks for the requesting user.
+func (s *Server) markWatching(userID string, thoughts []domain.Thought) {
+	watched := s.store.WatchedTaskIDs(userID)
+	if len(watched) == 0 {
+		return
+	}
+	for i := range thoughts {
+		thoughts[i].IsWatching = watched[thoughts[i].ID]
+	}
+}

internal/api/notify_test.go

@@ -0,0 +1,160 @@
+package api
+
+import (
+	"net/http"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/sandrodach/mindsift/internal/domain"
+)
+
+type sentNote struct{ channel, to, subject, text, html string }
+
+func notifyServer(t *testing.T) (*Server, *[]sentNote) {
+	t.Helper()
+	srv, _, _ := setupTestServer(t)
+	srv.cfg.NotifyDigestMinutes = 5
+	var sent []sentNote
+	srv.notifyEmailHook = func(to, subject, text, html string) error {
+		sent = append(sent, sentNote{channel: "email", to: to, subject: subject, text: text, html: html})
+		return nil
+	}
+	srv.notifyDiscordHook = func(url, heading string, items []notifyItem) error {
+		lines := make([]string, 0, len(items))
+		for _, it := range items {
+			lines = append(lines, it.text)
+		}
+		sent = append(sent, sentNote{channel: "discord", to: url, text: strings.Join(lines, "\n")})
+		return nil
+	}
+	return srv, &sent
+}
+
+func TestWatchedTaskChangesAreBundled(t *testing.T) {
+	srv, sent := notifyServer(t)
+	store := srv.store
+	router := srv.Router()
+	owner, ownerToken := newTestUser(t, store, "owner@example.com")
+	watcher, watcherToken := newTestUser(t, store, "watcher@example.com")
+	list, _ := store.CreateTaskList(owner.ID, "", "", "Haushalt", "🏠", "#000000")
+	task, _ := store.CreateThoughtWithDetails(owner.ID, "Fenster putzen", "normal", "manual", "", list.ID, "todo", "")
+	if _, err := store.AddTaskListShare(list.ID, "user", watcher.ID, "editor", owner.ID); err != nil {
+		t.Fatal(err)
+	}
+	if rec := sessionCall(router, "POST", "/api/v1/tasks/"+task.ID+"/watch", watcherToken, "", ""); rec.Code != http.StatusOK {
+		t.Fatalf("watch: %d %s", rec.Code, rec.Body.String())
+	}
+	_, strangerToken := newTestUser(t, store, "fremd@example.com")
+	if rec := sessionCall(router, "POST", "/api/v1/tasks/"+task.ID+"/watch", strangerToken, "", ""); rec.Code != http.StatusNotFound {
+		t.Fatalf("stranger watch: want 404, got %d", rec.Code)
+	}
+
+	// Two changes by the owner within the window → one bundled mail for the watcher, none for the owner
+	sessionCall(router, "PATCH", "/api/v1/thoughts/"+task.ID, ownerToken, `{"content":"Fenster putzen (innen)"}`, "")
+	sessionCall(router, "PATCH", "/api/v1/thoughts/"+task.ID, ownerToken, `{"isCompleted":true}`, "")
+	srv.flushNotifications(time.Now())
+	if len(*sent) != 0 {
+		t.Fatalf("nothing may go out before the window ends: %+v", *sent)
+	}
+	srv.flushNotifications(time.Now().Add(6 * time.Minute))
+	var mails []sentNote
+	for _, n := range *sent {
+		if n.channel == "email" {
+			mails = append(mails, n)
+		}
+	}
+	if len(mails) != 1 || mails[0].to != "watcher@example.com" || !strings.Contains(mails[0].text, "Text geändert") ||
+		!strings.Contains(mails[0].text, "erledigt") || !strings.Contains(mails[0].html, "<html") {
+		t.Fatalf("expected one bundled HTML mail to the watcher, got %+v", *sent)
+	}
+	*sent = nil
+	srv.flushNotifications(time.Now().Add(20 * time.Minute))
+	if len(*sent) != 0 {
+		t.Fatal("queue must be empty after sending")
+	}
+}
+
+func TestOwnChangesPauseAndChannels(t *testing.T) {
+	srv, sent := notifyServer(t)
+	store := srv.store
+	router := srv.Router()
+	me, myToken := newTestUser(t, store, "me@example.com")
+	task, _ := store.CreateThoughtWithDetails(me.ID, "Steuer", "normal", "manual", "", "", "todo", "")
+	_ = store.WatchTask(task.ID, me.ID, true)
+
+	// Own change on a watched task: nothing …
+	sessionCall(router, "PATCH", "/api/v1/thoughts/"+task.ID, myToken, `{"priority":"high"}`, "")
+	srv.flushNotifications(time.Now().Add(10 * time.Minute))
+	if len(*sent) != 0 {
+		t.Fatalf("own change must not notify: %+v", *sent)
+	}
+	// … unless asked for, then only over the chosen channel
+	set := store.NotificationSettingsOf(me.ID)
+	set.IncludeOwnWatched = true
+	set.Events.Watched = domain.ChannelChoice{Discord: true}
+	_ = store.SetNotificationSettings(me.ID, set)
+	hook := "https://discord.com/api/webhooks/1/x"
+	_, _ = store.UpdateUserFull(me.ID, nil, nil, nil, nil, nil, nil, &hook, nil, nil, nil)
+	sessionCall(router, "PATCH", "/api/v1/thoughts/"+task.ID, myToken, `{"priority":"low"}`, "")
+	srv.flushNotifications(time.Now().Add(10 * time.Minute))
+	if len(*sent) != 1 || (*sent)[0].channel != "discord" {
+		t.Fatalf("expected one Discord message, got %+v", *sent)
+	}
+
+	// Paused: nothing at all
+	*sent = nil
+	set.Paused = true
+	_ = store.SetNotificationSettings(me.ID, set)
+	sessionCall(router, "PATCH", "/api/v1/thoughts/"+task.ID, myToken, `{"priority":"urgent"}`, "")
+	srv.flushNotifications(time.Now().Add(10 * time.Minute))
+	if len(*sent) != 0 {
+		t.Fatalf("paused must send nothing: %+v", *sent)
+	}
+
+	// Settings round trip over the profile API
+	rec := sessionCall(router, "PATCH", "/api/v1/auth/settings", myToken, `{"notificationSettings":{"paused":false,"events":{"shared":{"email":false,"discord":true}},"dailySummary":{"enabled":true,"time":"6:5"}}}`, "")
+	if rec.Code != http.StatusOK || !strings.Contains(rec.Body.String(), `"time":"07:00"`) || !strings.Contains(rec.Body.String(), `"shared":{"email":false,"discord":true}`) {
+		t.Fatalf("settings: %d %s", rec.Code, rec.Body.String())
+	}
+}
+
+func TestDailySummary(t *testing.T) {
+	srv, sent := notifyServer(t)
+	store := srv.store
+	me, _ := newTestUser(t, store, "summary@example.com")
+	now := time.Date(2026, 10, 30, 7, 0, 30, 0, time.Local)
+	set := store.NotificationSettingsOf(me.ID)
+	set.DailySummary = domain.DailySummary{Enabled: true, Time: "07:00", Email: true}
+	_ = store.SetNotificationSettings(me.ID, set)
+
+	srv.sendDailySummaries(now)
+	if len(*sent) != 0 {
+		t.Fatal("nothing due → no summary")
+	}
+	for _, td := range [][2]string{{"Altlast", "2026-10-28"}, {"Zahnarzt", "2026-10-30T15:30"}, {"Müll raus", "2026-10-31"}, {"Später", "2026-11-04"}} {
+		th, _ := store.CreateThoughtWithDetails(me.ID, td[0], "normal", "manual", td[1], "", "todo", "")
+		if _, err := store.UpdateThoughtTriage(me.ID, th.ID, "keep", "task", "", td[1], ""); err != nil { // triaged into a task
+			t.Fatal(err)
+		}
+	}
+
+	srv.sendDailySummaries(now.Add(-2 * time.Minute)) // before the chosen time
+	if len(*sent) != 0 {
+		t.Fatal("no summary before the chosen time")
+	}
+	srv.sendDailySummaries(now)
+	if len(*sent) != 1 {
+		t.Fatalf("expected one summary, got %d", len(*sent))
+	}
+	text := (*sent)[0].text
+	for _, want := range []string{"Überfällig", "Altlast", "Heute, 15:30 Uhr: Zahnarzt", "Morgen: Müll raus", "1 weitere"} {
+		if !strings.Contains(text, want) {
+			t.Fatalf("summary lacks %q:\n%s", want, text)
+		}
+	}
+	srv.sendDailySummaries(now.Add(5 * time.Minute))
+	if len(*sent) != 1 {
+		t.Fatal("only one summary per day")
+	}
+}

internal/api/server.go

@@ -34,6 +34,10 @@ type Server struct {
 	streamTickets streamTickets // one-time tickets for WebSocket/SSE (streamticket.go)
 	loginGuard    *loginGuard   // brute-force protection (loginguard.go)
 	voice         *voiceService // self-hosted speech recognition (voice.go)
+
+	// Replace the delivery of bundled notifications in tests (notify.go)
+	notifyEmailHook   func(to, subject, text, html string) error
+	notifyDiscordHook func(webhookURL, heading string, items []notifyItem) error
 }
 
 func NewServer(cfg *config.Config, store *storage.Store, wsHub *ws.Hub, staticFS fs.FS) *Server {
@@ -62,6 +66,7 @@ func NewServer(cfg *config.Config, store *storage.Store, wsHub *ws.Hub, staticFS
 	}
 	if !cfg.DemoMode {
 		go srv.startAlarmTicker() // the demo sends nothing (FLAW-33)
+		go srv.startNotificationJobs()
 		go srv.startBackupScheduler()
 	}
 	return srv
@@ -136,6 +141,8 @@ func (s *Server) Router() http.Handler {
 		r.Post("/api/v1/documents/{id}/media/fetch", s.notInDemo(s.handleFetchMedia))
 		r.Get("/api/v1/media/{id}", s.handleGetMedia)
 		r.Post("/api/v1/documents/{id}/extract", s.handleExtractBranch)
+		r.Post("/api/v1/tasks/{id}/watch", s.handleWatchTask)
+		r.Delete("/api/v1/tasks/{id}/watch", s.handleWatchTask)
 		r.Post("/api/v1/documents/{id}/extract/undo", s.handleUndoExtract)
 		r.Post("/api/v1/documents/{id}/merge", s.handleMergeDocuments)
 		r.Post("/api/v1/documents/{id}/merge/undo", s.handleUndoMerge)