refactor(apps): 主题系统迁移至 ColorScheme + 扩展架构并支持 Dark Mode

apps/lib/features/home/presentation/widgets/home_unread_badge.dart

@@ -12,6 +12,8 @@ class HomeUnreadBadge extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
+
     return AppPressable(
       onTap: onTap,
       child: Container(
@@ -20,11 +22,11 @@ class HomeUnreadBadge extends StatelessWidget {
           vertical: AppSpacing.sm,
         ),
         decoration: BoxDecoration(
-          color: AppColors.blue600,
+          color: colorScheme.primary,
           borderRadius: BorderRadius.circular(AppRadius.full),
           boxShadow: [
             BoxShadow(
-              color: AppColors.slate900.withValues(alpha: 0.18),
+              color: colorScheme.shadow.withValues(alpha: 0.18),
               blurRadius: AppRadius.md,
               offset: const Offset(0, AppSpacing.xs),
             ),
@@ -32,9 +34,9 @@ class HomeUnreadBadge extends StatelessWidget {
         ),
         child: Text(
           context.l10n.homeUnreadMessages(count),
-          style: const TextStyle(
-            color: AppColors.white,
-            fontSize: 12,
+          style: TextStyle(
+            color: colorScheme.onPrimary,
+            fontSize: AppSpacing.md,
             fontWeight: FontWeight.w600,
           ),
         ),