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>

cmd/server/main.go

@@ -56,7 +56,7 @@ func main() {
 	}
 
 	// Seed SMTP defaults from environment variables into DB if not yet configured in DB
-	store.SeedSMTPDefaultsFromEnv(cfg.SMTPHost, cfg.SMTPPort, cfg.SMTPUser, cfg.SMTPPass, cfg.SMTPFrom, cfg.SMTPTLS, cfg.SMTPSkipVerify)
+	store.SeedSMTPDefaultsFromEnv(cfg.SMTPHost, cfg.SMTPPort, cfg.SMTPUser, cfg.SMTPPass, cfg.SMTPFrom, cfg.SMTPFromName, cfg.SMTPTLS, cfg.SMTPSkipVerify)
 
 	wsHub := ws.NewHub()