feat(flutter): 应用浅色暖橙视觉主题

lib/pages/discover/widgets/ranking_section.dart

@@ -135,7 +135,7 @@ class _RankingSectionState extends State<RankingSection> {
     final selected = logic.board == board;
     return Material(
       key: key,
-      color: selected ? AppColors.blue : AppColors.raised,
+      color: selected ? AppColors.blue : AppColors.card,
       borderRadius: BorderRadius.circular(999),
       clipBehavior: Clip.antiAlias,
       child: InkWell(
@@ -145,7 +145,7 @@ class _RankingSectionState extends State<RankingSection> {
           child: Text(
             label,
             style: TextStyle(
-              color: selected ? AppColors.onPrimary : AppColors.muted,
+              color: selected ? AppColors.onPrimary : AppColors.onSurface,
               fontSize: 9,
               fontWeight: FontWeight.w700,
             ),