simplified code across the app and consolidated duplicated helpers

lib/notification/notification_controller.dart

@@ -15,7 +15,7 @@ import '../widget/info_dialog.dart';
 import 'notification_tasks.dart';
 
 /// Bridges FCM lifecycle callbacks to the push pipeline. Background messages are
-/// handled directly by [PushMessageHandler.onBackgroundMessage]; this class
+/// handled directly by `pushOnBackgroundMessage`; this class
 /// covers the foreground and app-opened paths where a [BuildContext] is
 /// available.
 class NotificationController {

lib/notification/notification_tasks.dart

@@ -27,17 +27,13 @@ class NotificationTasks {
     }
   }
 
-  /// Per-chat tag scheme — canonical definition lives beside the stacked
-  /// notification id in chat_thread_store.dart.
-  static String chatTag(String chatToken) => chatNotificationTag(chatToken);
-
   /// Removes tray notifications belonging to [chatToken]. Eraser handles
   /// iOS (where the plugin's `getActiveNotifications` returns null ids
   /// for FCM posts and can't cancel them); the local-notifications sweep
   /// handles Android and acts as a fallback while Eraser's native side
   /// isn't built in yet.
   static Future<void> clearNotificationsForChat(String chatToken) async {
-    final tag = chatTag(chatToken);
+    final tag = chatNotificationTag(chatToken);
     try {
       await Eraser.clearAppNotificationsByTag(tag);
     } on MissingPluginException {