migrated Marianum Message module to the Marianum-Connect API and implemented push notification deep linking

lib/app.dart

@@ -93,6 +93,13 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     NotificationTasks.navigateToTalk(context, chatToken: token);
   }
 
+  void _onNewsletterTapPending() {
+    final id = PushTapRouter.pendingNewsletterId.value;
+    if (id == null || !mounted) return;
+    PushTapRouter.pendingNewsletterId.value = null;
+    AppRoutes.openNewsletterById(context, id: id);
+  }
+
   Future<void> _handlePendingWidgetNavigation() async {
     final pending = await WidgetNavigation.consumePendingTimetableTap();
     if (!pending || !mounted) return;
@@ -191,6 +198,7 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     // Android renders pushes locally, so a tap arrives via the local
     // notifications callback (PushTapRouter) rather than onMessageOpenedApp.
     PushTapRouter.pendingChatToken.addListener(_onPushTapPending);
+    PushTapRouter.pendingNewsletterId.addListener(_onNewsletterTapPending);
 
     _onMessageSub = FirebaseMessaging.onMessage.listen((message) {
       if (!mounted) return;
@@ -221,6 +229,7 @@ class _AppState extends State<App> with WidgetsBindingObserver {
     _onMessageOpenedAppSub?.cancel();
     _fcmTokenRefreshSub?.cancel();
     PushTapRouter.pendingChatToken.removeListener(_onPushTapPending);
+    PushTapRouter.pendingNewsletterId.removeListener(_onNewsletterTapPending);
     ShareIntentListener.pending.removeListener(_handlePendingShare);
     ShareIntentListener.instance.detach();
     Main.bottomNavigator.removeListener(_onTabControllerChanged);