feat(flutter): 应用浅色暖橙视觉主题

lib/pages/discover/widgets/discover_header.dart

@@ -88,12 +88,12 @@ class DiscoverHeader extends StatelessWidget {
             gradient: LinearGradient(
               begin: Alignment.topLeft,
               end: Alignment.bottomRight,
-              colors: [Color(0xFF6A5CFF), AppColors.blue],
+              colors: [AppColors.secondary, AppColors.blue],
             ),
           ),
           child: const Icon(
             Icons.person_rounded,
-            color: AppColors.onSurface,
+            color: AppColors.onPrimary,
             size: 18,
           ),
         ),
@@ -124,7 +124,7 @@ class _HeaderIcon extends StatelessWidget {
         onPressed: onTap,
         padding: EdgeInsets.zero,
         style: IconButton.styleFrom(
-          backgroundColor: const Color(0xFF2C2D33),
+          backgroundColor: AppColors.raised,
           foregroundColor: AppColors.onSurface,
         ),
         icon: Icon(icon, size: 18),