feat(flutter): 统一空列表占位组件

test/notice/notices_page_test.dart

@@ -6,6 +6,7 @@ import 'package:fruitshorts/core/data/models/notice.dart';
 import 'package:fruitshorts/core/data/remote/api_client.dart';
 import 'package:fruitshorts/core/data/repositories/notice_repository.dart';
 import 'package:fruitshorts/core/formatting/localized_date_time.dart';
+import 'package:fruitshorts/core/widgets/empty_state.dart';
 import 'package:fruitshorts/l10n/app_localizations.dart';
 import 'package:fruitshorts/pages/notices/notices_page.dart';
 import 'package:provider/provider.dart';
@@ -39,6 +40,7 @@ void main() {
     );
 
     expect(find.byKey(const Key('notices-empty')), findsOneWidget);
+    expect(find.byType(EmptyState), findsOneWidget);
   });
 
   testWidgets('should_show_backend_error_and_retry_when_page_fails', (