feat(flutter): 统一空列表占位组件

lib/pages/notices/notices_page.dart

@@ -12,6 +12,7 @@ import '../../core/formatting/error_text.dart';
 import '../../core/formatting/localized_date_time.dart';
 import '../../core/theme/app_colors.dart';
 import '../../core/theme/app_theme.dart';
+import '../../core/widgets/empty_state.dart';
 import '../../l10n/app_localizations.dart';
 
 /// Anonymous system notice list with pagination and detail dialog.
@@ -109,12 +110,11 @@ class _NoticesPageState extends State<NoticesPage> {
           children: [
             SizedBox(
               height: MediaQuery.sizeOf(context).height * 0.7,
-              child: Center(
+              child: EmptyState(
                 key: const Key('notices-empty'),
-                child: Text(
-                  l10n.noNotices,
-                  style: const TextStyle(color: AppColors.muted),
-                ),
+                icon: Icons.notifications_none_rounded,
+                title: l10n.noNotices,
+                subtitle: l10n.emptyHint,
               ),
             ),
           ],