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

lib/routing/app_routes.dart

@@ -131,13 +131,29 @@ class AppRoutes {
 
   static void openMarianumMessage(
     BuildContext context,
-    String basePath,
     MarianumMessage message,
   ) {
     pushScreen(
       context,
       withNavBar: false,
-      screen: MessageView(basePath: basePath, message: message),
+      screen: MessageView(id: message.id, title: message.name),
+    );
+  }
+
+  /// Opens a Marianum Message by id — used for push deep links where only the
+  /// id (and the notification title) are known.
+  static void openNewsletterById(
+    BuildContext context, {
+    required String id,
+    String? title,
+  }) {
+    pushScreen(
+      context,
+      withNavBar: false,
+      screen: MessageView(
+        id: id,
+        title: title == null || title.isEmpty ? 'Marianum Message' : title,
+      ),
     );
   }