feat(mail): sender display name (SMTP_FROM_NAME, default MindSift)

A bare SMTP_FROM address gets the display name in the From header; a name
already in SMTP_FROM wins, the envelope keeps the bare address. Also a
field in the admin mail settings.

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

internal/api/mail.go

@@ -20,8 +20,9 @@ import (
 // smtpSettings is the effective mail server configuration (admin settings, else environment).
 type smtpSettings struct {
 	Host, Port, User, Pass, From string
-	TLS                          bool // 465: implicit TLS, otherwise STARTTLS (required when set)
-	SkipVerify                   bool // accept self-signed / mismatching certificates
+	FromName                     string // display name when From is a bare address
+	TLS                          bool   // 465: implicit TLS, otherwise STARTTLS (required when set)
+	SkipVerify                   bool   // accept self-signed / mismatching certificates
 
 	authMech string // "" = automatic; "LOGIN" forces AUTH LOGIN (fallback after a refused PLAIN)
 }
@@ -46,13 +47,15 @@ func (s *Server) smtpSettings() (smtpSettings, error) {
 		cfg = smtpSettings{
 			Host: strings.TrimSpace(sys.SMTPHost), Port: strings.TrimSpace(sys.SMTPPort),
 			User: strings.TrimSpace(sys.SMTPUser), Pass: sys.SMTPPass, From: strings.TrimSpace(sys.SMTPFrom),
-			TLS: sys.SMTPTLS, SkipVerify: sys.SMTPSkipVerify,
+			FromName: strings.TrimSpace(sys.SMTPFromName),
+			TLS:      sys.SMTPTLS, SkipVerify: sys.SMTPSkipVerify,
 		}
 	} else if strings.TrimSpace(s.cfg.SMTPHost) != "" {
 		cfg = smtpSettings{
 			Host: strings.TrimSpace(s.cfg.SMTPHost), Port: strings.TrimSpace(s.cfg.SMTPPort),
 			User: strings.TrimSpace(s.cfg.SMTPUser), Pass: s.cfg.SMTPPass, From: strings.TrimSpace(s.cfg.SMTPFrom),
-			TLS: s.cfg.SMTPTLS, SkipVerify: s.cfg.SMTPSkipVerify,
+			FromName: strings.TrimSpace(s.cfg.SMTPFromName),
+			TLS:      s.cfg.SMTPTLS, SkipVerify: s.cfg.SMTPSkipVerify,
 		}
 	}
 	if cfg.Host == "" {
@@ -61,6 +64,9 @@ func (s *Server) smtpSettings() (smtpSettings, error) {
 	if cfg.Port == "" {
 		cfg.Port = "587"
 	}
+	if cfg.FromName == "" {
+		cfg.FromName = "MindSift"
+	}
 	if cfg.From == "" {
 		if strings.Contains(cfg.User, "@") {
 			cfg.From = cfg.User
@@ -96,6 +102,19 @@ func splitAddress(raw string) (envelope, header string, err error) {
 	return addr.Address, addr.String(), nil
 }
 
+// senderAddress is splitAddress for the sender: a bare address gets the display name, so mail clients
+// show "MindSift" instead of only the address. A name already in SMTP_FROM wins.
+func senderAddress(raw, name string) (envelope, header string, err error) {
+	addr, err := mail.ParseAddress(strings.TrimSpace(raw))
+	if err != nil {
+		return "", "", fmt.Errorf("ungültige E-Mail-Adresse %q", raw)
+	}
+	if addr.Name == "" {
+		addr.Name = strings.TrimSpace(name)
+	}
+	return addr.Address, addr.String(), nil
+}
+
 // 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 {
@@ -202,7 +221,7 @@ 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 {
-	fromAddr, fromHeader, err := splitAddress(cfg.From)
+	fromAddr, fromHeader, err := senderAddress(cfg.From, cfg.FromName)
 	if err != nil {
 		return &smtpStepError{"Absender", err}
 	}