add notification, fix appbar,fix style subscription

lib/presentation/state/notifications_state.dart

@@ -0,0 +1,27 @@
+import '../../domain/entities/client_notification.dart';
+
+enum NotificationsStatus { initial, loading, success, failure }
+
+class NotificationsState {
+  final NotificationsStatus status;
+  final List<ClientNotification> notifications;
+  final String? errorMessage;
+
+  const NotificationsState({
+    this.status = NotificationsStatus.initial,
+    this.notifications = const [],
+    this.errorMessage,
+  });
+
+  NotificationsState copyWith({
+    NotificationsStatus? status,
+    List<ClientNotification>? notifications,
+    String? errorMessage,
+  }) {
+    return NotificationsState(
+      status: status ?? this.status,
+      notifications: notifications ?? this.notifications,
+      errorMessage: errorMessage ?? this.errorMessage,
+    );
+  }
+}