style(theme): 客户端切换深色视觉风格

lib/pages/discover/widgets/drama_grid.dart

@@ -23,8 +23,8 @@ const double _tagChipFontSize = 11;
 const double _heatFontSize = 9;
 const double _heatIconSize = 11;
 const int _maxTags = 3;
-const Color _heatBackground = Color(0x99000000);
-const Color _tagChipBackground = Color(0xFFF4F1EE);
+const Color _heatBackground = AppColors.overlayMedium;
+const Color _tagChipBackground = AppColors.raised;
 final RegExp _tagSplitter = RegExp(r'[,/、·]');
 
 /// 剧场/分类页共用的双列剧目网格。
@@ -231,11 +231,11 @@ class _DiscoverCoverImage extends StatelessWidget {
 
   Widget _placeholder() {
     return const ColoredBox(
-      color: AppColors.card,
+      color: AppColors.raised,
       child: Center(
         child: Icon(
           Icons.image_not_supported_outlined,
-          color: AppColors.muted,
+          color: AppColors.subtle,
           size: 32,
         ),
       ),