auto-sync token on refresh and cold start

lib/services/notification/firebase_api.dart

@@ -1,6 +1,8 @@
 import 'package:didvan/models/notification_message.dart';
 import 'package:didvan/services/app_home_widget/home_widget_repository.dart';
 import 'package:didvan/services/app_initalizer.dart';
+import 'package:didvan/services/auth/auth_api_service.dart';
+import 'package:didvan/services/auth/token_storage.dart';
 import 'package:didvan/services/notification/notification_service.dart';
 import 'package:didvan/services/storage/storage.dart';
 import 'package:firebase_messaging/firebase_messaging.dart';
@@ -88,6 +90,46 @@ class FirebaseApi {
     });
 
     FirebaseMessaging.onMessage.listen((event) => handleMessage(event));
+
+    // Push the current token to auth-service whenever it changes (Firebase
+    // rotates it every few months, or after app reinstall, or after the
+    // user clears app data). Without this we'd lose push delivery for
+    // already-logged-in users until they explicitly logged in again.
+    FirebaseMessaging.instance.onTokenRefresh.listen((newToken) async {
+      fcmToken = newToken;
+      await _syncTokenToServer(newToken);
+    });
+
+    // Also sync once on every cold start: covers the case where the user
+    // already logged in on a previous build and the server has a stale or
+    // missing token.
+    if (fcmToken != null && fcmToken!.isNotEmpty) {
+      await _syncTokenToServer(fcmToken!);
+    }
+  }
+
+  /// Push the FCM token up to auth-service so push notifications can reach
+  /// this device. Safely no-ops when the user isn't logged in (no userId
+  /// yet) — we'll catch them on the next cold start once they sign in.
+  Future<void> _syncTokenToServer(String token) async {
+    try {
+      final userId = TokenStorage.userId;
+      if (userId == null || userId.isEmpty) {
+        if (kDebugMode) {
+          print('FCM token refresh: skipping — user not logged in yet');
+        }
+        return;
+      }
+      final result = await AuthApiService.instance.updateUser(
+        id: userId,
+        data: {'firebaseToken': token},
+      );
+      if (kDebugMode) {
+        print('FCM token pushed to server: success=${result.isSuccess}');
+      }
+    } catch (e) {
+      if (kDebugMode) print('FCM token sync failed: $e');
+    }
   }
 
   void handleMessage(RemoteMessage? message) async {