feat: Introduce comprehensive unit tests for models and BLoCs using mockito and bloc_test, and refine TripBloc error handling.

lib/blocs/auth/auth_bloc.dart

@@ -31,14 +31,18 @@ import '../../services/notification_service.dart';
 class AuthBloc extends Bloc<AuthEvent, AuthState> {
   /// Repository for authentication operations.
   final AuthRepository _authRepository;
+  final NotificationService _notificationService;
 
   /// Creates an [AuthBloc] with the provided [authRepository].
   ///
   /// The bloc starts in the [AuthInitial] state and registers event handlers
   /// for all supported authentication events.
-  AuthBloc({required AuthRepository authRepository})
-    : _authRepository = authRepository,
-      super(AuthInitial()) {
+  AuthBloc({
+    required AuthRepository authRepository,
+    NotificationService? notificationService,
+  }) : _authRepository = authRepository,
+       _notificationService = notificationService ?? NotificationService(),
+       super(AuthInitial()) {
     on<AuthCheckRequested>(_onAuthCheckRequested);
     on<AuthSignInRequested>(_onSignInRequested);
     on<AuthSignUpRequested>(_onSignUpRequested);
@@ -71,7 +75,7 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
 
         if (user != null) {
           // Save FCM Token on auto-login
-          await NotificationService().saveTokenToFirestore(user.id!);
+          await _notificationService.saveTokenToFirestore(user.id!);
           emit(AuthAuthenticated(user: user));
         } else {
           emit(AuthUnauthenticated());