style(theme): 客户端切换深色视觉风格

lib/core/widgets/subpage_header.dart

@@ -16,9 +16,6 @@ const double _iconSize = 22;
 const double _iconWeight = 600;
 const double _borderWidth = 1;
 const double _shadowBlur = 8;
-const Color _lightShadowColor = Color(0x14000000);
-const Color _darkBackground = Color(0x59000000);
-const Color _darkShadowColor = Color(0x33000000);
 const Offset _lightShadowOffset = Offset(0, 2);
 
 /// 二级页面统一圆形操作按钮，返回、分享和更多共用同一尺寸与表面样式。
@@ -52,14 +49,14 @@ class AppSubpageCircleButton extends StatelessWidget {
             shape: BoxShape.circle,
             boxShadow: [
               BoxShadow(
-                color: dark ? _darkShadowColor : _lightShadowColor,
+                color: dark ? AppColors.shadowSoft : AppColors.shadowSubtle,
                 blurRadius: _shadowBlur,
                 offset: dark ? Offset.zero : _lightShadowOffset,
               ),
             ],
           ),
           child: Material(
-            color: dark ? _darkBackground : AppColors.card,
+            color: dark ? AppColors.headerScrim : AppColors.card,
             shape: CircleBorder(
               side: dark
                   ? BorderSide.none
@@ -75,7 +72,7 @@ class AppSubpageCircleButton extends StatelessWidget {
               child: Center(
                 child: Icon(
                   icon,
-                  color: dark ? Colors.white : AppColors.onSurface,
+                  color: AppColors.onSurface,
                   size: _iconSize,
                   weight: _iconWeight,
                 ),
@@ -134,8 +131,8 @@ class AppSubpageHeader extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final foreground = dark ? Colors.white : AppColors.onSurface;
-    final secondary = dark ? Colors.white70 : AppColors.muted;
+    final foreground = AppColors.onSurface;
+    final secondary = AppColors.muted;
     return SizedBox(
       key: const Key('subpage-header'),
       height: subtitle == null ? _height : _heightWithSubtitle,