Controller v0.7.2: notification preferences sync to hub

- SyncPreferences() method on Notifier: POST to hub /api/v1/preferences
- IsEnabled() getter for hub connectivity check
- settingsNotificationsHandler: sync to hub after local save (3 flash message variants)
- Startup sync: non-blocking goroutine pushes prefs to hub on boot (DB rebuild recovery)
- Updated CONTEXT.md, README.md with v0.7.2 changes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/internal/web/handlers.go

@@ -371,8 +371,18 @@ func (s *Server) settingsNotificationsHandler(w http.ResponseWriter, r *http.Req
 
 	s.logger.Printf("[INFO] Notification preferences updated: email=%s, events=%v", email, enabledEvents)
 
+	// Sync preferences to hub
 	data := s.settingsData()
-	data["NotificationSuccess"] = "Értesítési beállítások mentve."
+	if s.notifier != nil && s.notifier.IsEnabled() {
+		if err := s.notifier.SyncPreferences(email, enabledEvents); err != nil {
+			s.logger.Printf("[WARN] Failed to sync preferences to hub: %v", err)
+			data["NotificationSuccess"] = fmt.Sprintf("Értesítési beállítások mentve (helyi). A központi szinkronizálás sikertelen: %v", err)
+		} else {
+			data["NotificationSuccess"] = "Értesítési beállítások mentve."
+		}
+	} else {
+		data["NotificationSuccess"] = "Értesítési beállítások mentve."
+	}
 	s.render(w, "settings", data)
 }