added guardian letters with chat and multiple answer functionalities

lib/routing/app_routes.dart

@@ -26,6 +26,7 @@ import '../view/pages/marianum_message/marianum_message_view.dart';
 import '../view/pages/more/feedback/feedback_dialog.dart';
 import '../view/pages/more/roomplan/roomplan.dart';
 import '../view/pages/more/share/qr_share_view.dart';
+import '../view/pages/parent_letters/parent_letter_view.dart';
 import '../view/pages/settings/chat_background_settings_page.dart';
 import '../view/pages/settings/modules_settings_page.dart';
 import '../view/pages/settings/settings.dart';
@@ -203,6 +204,12 @@ class AppRoutes {
     );
   }
 
+  /// Opens a parent letter by id — from the inbox as well as from push deep
+  /// links, where only the id is known.
+  static void openParentLetter(BuildContext context, {required String id}) {
+    pushScreen(context, withNavBar: false, screen: ParentLetterView(id: id));
+  }
+
   /// Opens a ticker page (CONTENT or PROXIED_FILE) as a standalone detail
   /// screen. Used for deep links from outside the ticker module — inside the
   /// module pages open in-place instead.