feat(flutter): 增加关键操作震动反馈

lib/pages/downloads/downloads_page.dart

@@ -11,6 +11,7 @@ import '../../core/data/services/auth_controller.dart';
 import '../../core/data/services/download_controller.dart';
 import '../../core/formatting/error_text.dart';
 import '../../core/formatting/localized_date_time.dart';
+import '../../core/platform/haptics.dart';
 import '../../core/theme/app_colors.dart';
 import '../../core/theme/app_theme.dart';
 import '../../core/widgets/auth_gate.dart';
@@ -166,6 +167,7 @@ class _DownloadsBody extends StatelessWidget {
   }
 
   Future<void> _remove(BuildContext context, String episodeId) async {
+    unawaited(context.read<Haptics>().mediumImpact());
     final ok = await downloads.remove(episodeId);
     if (ok || !context.mounted) return;
     _showMessage(context, AppLocalizations.of(context)!.downloadDeleteFailed);
@@ -191,6 +193,9 @@ class _DownloadsBody extends StatelessWidget {
       ),
     );
     if (confirmed != true) return;
+    if (context.mounted) {
+      unawaited(context.read<Haptics>().mediumImpact());
+    }
     final ok = await downloads.clear();
     if (!ok && context.mounted) {
       _showMessage(context, l10n.downloadClearFailed);