feat(app): 搜索改为调用后端并渲染卡片结果

lib/pages/discover/widgets/home_drama_grid.dart

@@ -8,6 +8,9 @@ class _HomeDramaGrid extends StatelessWidget {
     required this.categories,
     required this.dramas,
     required this.searching,
+    required this.searchLoading,
+    required this.searchError,
+    required this.onRetrySearch,
     required this.onOpen,
   });
 
@@ -15,6 +18,9 @@ class _HomeDramaGrid extends StatelessWidget {
   final CategoryController categories;
   final List<Drama> dramas;
   final bool searching;
+  final bool searchLoading;
+  final String? searchError;
+  final VoidCallback onRetrySearch;
   final ValueChanged<Drama> onOpen;
 
   @override
@@ -37,6 +43,29 @@ class _HomeDramaGrid extends StatelessWidget {
         ),
       );
     }
+    if (searching && searchLoading) {
+      return const SliverFillRemaining(
+        hasScrollBody: false,
+        child: Center(
+          child: CircularProgressIndicator(
+            key: Key('discover-search-loading'),
+            strokeWidth: 2,
+          ),
+        ),
+      );
+    }
+    if (searching && searchError != null) {
+      return _fill(
+        EmptyState(
+          key: const Key('discover-search-error'),
+          icon: Icons.cloud_off_rounded,
+          title: errorText(l10n, searchError, l10n.searchFailed),
+          actionLabel: l10n.retry,
+          actionKey: const Key('discover-search-retry'),
+          onAction: onRetrySearch,
+        ),
+      );
+    }
     if (dramas.isEmpty) {
       return _fill(
         EmptyState(