feat(workspace): journal with one note per day and a calendar

- journal_days (migration 8) maps a person's day to an ordinary note;
  GET /journal lists the days, POST /journal/{date} opens or creates one
- the journal sits on top of the notes sidebar: days below each other
  (today first, older ones load while scrolling), a calendar with month
  and year picker follows the day in view and jumps to any day
- the header shares the day in view; journal notes stay out of the folder
  tree; can be switched off per device under Darstellung

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

internal/api/journal.go

@@ -0,0 +1,70 @@
+package api
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/sandrodach/mindsift/internal/auth"
+)
+
+// Journal: one ordinary note per day, opened (and created on first use) by date. The web app shows the
+// days below each other with a calendar; the notes can be shared and searched like any other.
+
+var journalMu sync.Mutex // one creation at a time, so a day never gets two notes
+
+var (
+	journalWeekdays = []string{"Sonntag", "Montag", "Dienstag", "Mittwoch", "Donnerstag", "Freitag", "Samstag"}
+	journalMonths   = []string{"Januar", "Februar", "März", "April", "Mai", "Juni", "Juli", "August", "September", "Oktober", "November", "Dezember"}
+)
+
+// journalTitle: "Freitag, 30. Oktober 2026"
+func journalTitle(day time.Time) string {
+	return fmt.Sprintf("%s, %d. %s %d", journalWeekdays[day.Weekday()], day.Day(), journalMonths[day.Month()-1], day.Year())
+}
+
+func (s *Server) handleGetJournal(w http.ResponseWriter, r *http.Request) {
+	days, err := s.store.JournalDays(auth.GetUserID(r.Context()))
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "Journal konnte nicht geladen werden")
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]interface{}{"days": days})
+}
+
+// handleOpenJournalDay returns the note of a day and creates it when there is none yet.
+func (s *Server) handleOpenJournalDay(w http.ResponseWriter, r *http.Request) {
+	userID := auth.GetUserID(r.Context())
+	date := chi.URLParam(r, "date")
+	day, err := time.Parse("2006-01-02", date)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "Ungültiges Datum (erwartet JJJJ-MM-TT)")
+		return
+	}
+	journalMu.Lock()
+	defer journalMu.Unlock()
+	docID, err := s.store.JournalDocID(userID, date)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "Journal konnte nicht geladen werden")
+		return
+	}
+	if docID != "" {
+		if doc, err := s.store.GetDocumentByID(userID, docID); err == nil {
+			writeJSON(w, http.StatusOK, doc)
+			return
+		}
+	}
+	doc, err := s.store.CreateDocument(userID, "", journalTitle(day), "📅", "", nil, nil, false)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "Journal-Tag konnte nicht angelegt werden")
+		return
+	}
+	if err := s.store.SetJournalDay(userID, date, doc.ID); err != nil {
+		writeError(w, http.StatusInternalServerError, "Journal-Tag konnte nicht angelegt werden")
+		return
+	}
+	s.broadcastDocToAuthorizedUsers(doc.ID, "DOC_CREATED")
+	writeJSON(w, http.StatusCreated, doc)
+}

internal/api/journal_test.go

@@ -0,0 +1,78 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"testing"
+	"time"
+)
+
+func TestJournalDayIsCreatedOnceAndListed(t *testing.T) {
+	srv, store, _ := setupTestServer(t)
+	router := srv.Router()
+	me, token := newTestUser(t, store, "journal@example.com")
+
+	rec := sessionCall(router, "POST", "/api/v1/journal/2026-10-30", token, "", "")
+	if rec.Code != http.StatusCreated {
+		t.Fatalf("create: %d %s", rec.Code, rec.Body.String())
+	}
+	var doc struct {
+		ID, Title, Icon string
+	}
+	_ = json.Unmarshal(rec.Body.Bytes(), &doc)
+	if doc.Title != "Freitag, 30. Oktober 2026" || doc.Icon != "📅" {
+		t.Fatalf("unexpected note: %+v", doc)
+	}
+
+	// Opening the same day again returns the same note
+	rec = sessionCall(router, "POST", "/api/v1/journal/2026-10-30", token, "", "")
+	var again struct{ ID string }
+	_ = json.Unmarshal(rec.Body.Bytes(), &again)
+	if rec.Code != http.StatusOK || again.ID != doc.ID {
+		t.Fatalf("second open: %d id %s want %s", rec.Code, again.ID, doc.ID)
+	}
+
+	rec = sessionCall(router, "GET", "/api/v1/journal", token, "", "")
+	var list struct {
+		Days []struct {
+			Date, DocID string
+			Empty       bool
+		}
+	}
+	_ = json.Unmarshal(rec.Body.Bytes(), &list)
+	if len(list.Days) != 1 || list.Days[0].Date != "2026-10-30" || list.Days[0].DocID != doc.ID || !list.Days[0].Empty {
+		t.Fatalf("list: %s", rec.Body.String())
+	}
+
+	// Other people have their own journal
+	_, otherToken := newTestUser(t, store, "andere@example.com")
+	rec = sessionCall(router, "GET", "/api/v1/journal", otherToken, "", "")
+	if rec.Code != http.StatusOK || rec.Body.String() == "" {
+		t.Fatalf("other list: %d", rec.Code)
+	}
+	_ = json.Unmarshal(rec.Body.Bytes(), &list)
+	if len(list.Days) != 0 {
+		t.Fatalf("other user must not see my journal: %+v", list.Days)
+	}
+
+	// A day whose note went to the trash gets a fresh note
+	if err := store.DeleteDocument(me.ID, doc.ID); err != nil {
+		t.Fatalf("trash: %v", err)
+	}
+	rec = sessionCall(router, "POST", "/api/v1/journal/2026-10-30", token, "", "")
+	_ = json.Unmarshal(rec.Body.Bytes(), &again)
+	if rec.Code != http.StatusCreated || again.ID == doc.ID {
+		t.Fatalf("after trash: %d id %s", rec.Code, again.ID)
+	}
+
+	if rec := sessionCall(router, "POST", "/api/v1/journal/30.10.2026", token, "", ""); rec.Code != http.StatusBadRequest {
+		t.Fatalf("bad date: want 400, got %d", rec.Code)
+	}
+}
+
+func TestJournalTitle(t *testing.T) {
+	day := time.Date(2026, 3, 1, 0, 0, 0, 0, time.UTC)
+	if got := journalTitle(day); got != "Sonntag, 1. März 2026" {
+		t.Fatalf("got %q", got)
+	}
+}

internal/api/server.go

@@ -217,6 +217,8 @@ func (s *Server) Router() http.Handler {
 		r.Get("/api/v1/workspace/tags/{tag}", s.handleGetTagDetails)
 		r.Put("/api/v1/workspace/tags/{tag}/note", s.handleUpdateTagPageNote)
 
+		r.Get("/api/v1/journal", s.handleGetJournal)
+		r.Post("/api/v1/journal/{date}", s.handleOpenJournalDay)
 		r.Get("/api/v1/documents", s.handleGetDocuments)
 		r.Post("/api/v1/documents", s.handleCreateDocument)
 		r.Get("/api/v1/documents/{id}", s.handleGetDocument)