feat(ui): 更新品牌启动页与选集交互

lib/pages/downloads/downloads_page.dart

@@ -54,9 +54,9 @@ class _DownloadsPageState extends State<DownloadsPage> {
       data: AppTheme.dark(),
       child: Scaffold(
         key: const Key('downloads-page'),
-        backgroundColor: const Color(0xFF0B0C10),
+        backgroundColor: AppColors.ink,
         appBar: AppBar(
-          backgroundColor: const Color(0xFF0B0C10),
+          backgroundColor: AppColors.ink,
           foregroundColor: Colors.white,
           title: Text(l10n.downloads),
         ),
@@ -79,41 +79,17 @@ class _DownloadsBody extends StatelessWidget {
     if (downloads.loading && downloads.policy == null) {
       return const Center(child: CircularProgressIndicator());
     }
-    if (downloads.error != null && downloads.policy == null) {
-      return Center(
+    if (downloads.policy == null) {
+      return EmptyState(
         key: const Key('downloads-error'),
-        child: Padding(
-          padding: const EdgeInsets.symmetric(horizontal: 32),
-          child: Column(
-            mainAxisSize: MainAxisSize.min,
-            children: [
-              Text(
-                errorText(l10n, downloads.error, l10n.downloadsError),
-                textAlign: TextAlign.center,
-                style: const TextStyle(color: Colors.white70),
-              ),
-              const SizedBox(height: 14),
-              FilledButton(
-                key: const Key('downloads-retry'),
-                onPressed: () => unawaited(downloads.load()),
-                child: Text(l10n.retry),
-              ),
-            ],
-          ),
-        ),
-      );
-    }
-    final policy = downloads.policy;
-    if (policy == null) {
-      return Center(
-        key: const Key('downloads-error'),
-        child: FilledButton(
-          key: const Key('downloads-retry'),
-          onPressed: () => unawaited(downloads.load()),
-          child: Text(l10n.retry),
-        ),
+        icon: Icons.cloud_off_rounded,
+        title: errorText(l10n, downloads.error, l10n.downloadsError),
+        actionLabel: l10n.retry,
+        actionKey: const Key('downloads-retry'),
+        onAction: () => unawaited(downloads.load()),
       );
     }
+    final policy = downloads.policy!;
     return RefreshIndicator(
       onRefresh: downloads.load,
       child: ListView(