refactor(theme): 迁移主题感知颜色至 ThemeExtension

- 创建 AppThemeColors ThemeExtension 类，统一管理主题感知颜色（涨跌色、卡片背景、渐变等）
- 从 AppColorScheme 移除主题感知辅助函数，仅保留静态颜色常量
- 在 AppTheme 中注册 ThemeExtension，支持深色/浅色主题工厂
- 重构所有 UI 组件使用 context.appColors 访问主题颜色，替代硬编码的 AppColorScheme 方法调用
- 移除组件中重复的 isDark 判断逻辑，简化颜色获取方式
- 保持向后兼容性，所有现有功能不变

flutter_monisuo/lib/ui/components/glass_panel.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import '../../core/theme/app_spacing.dart';
+import '../../core/theme/app_theme_extension.dart';
 
 /// GlassPanel - 实心背景面板
 ///
@@ -55,11 +56,8 @@ class GlassPanel extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final isDark = Theme.of(context).brightness == Brightness.dark;
-    final bgColor = backgroundColor ??
-        (isDark ? colorScheme.surfaceContainer : colorScheme.surfaceContainerHigh);
-    final brColor = borderColor ?? colorScheme.outlineVariant.withOpacity(0.15);
+    final bgColor = backgroundColor ?? context.appColors.surfaceCard;
+    final brColor = borderColor ?? context.appColors.ghostBorder;
     final br = borderRadius ?? BorderRadius.circular(AppRadius.xl);
 
     Widget content = Container(
@@ -133,11 +131,9 @@ class GlassCard extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final isDark = Theme.of(context).brightness == Brightness.dark;
     final br = borderRadius ?? BorderRadius.circular(AppRadius.xl);
     final glowColor = neonGlowColor ??
-        colorScheme.primary.withOpacity(isDark ? 0.15 : 0.08);
+        context.colors.primary.withValues(alpha: context.appColors.glowOpacity);
 
     Widget card = GlassPanel(
       padding: padding ?? EdgeInsets.all(AppSpacing.md),
@@ -200,17 +196,14 @@ class GlassBottomSheet extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final colorScheme = Theme.of(context).colorScheme;
-    final isDark = Theme.of(context).brightness == Brightness.dark;
-
     return Container(
       decoration: BoxDecoration(
-        color: isDark ? colorScheme.surfaceContainer : colorScheme.surfaceContainerHigh,
+        color: context.appColors.surfaceCard,
         borderRadius: const BorderRadius.vertical(
           top: Radius.circular(AppRadius.xxl),
         ),
         border: Border.all(
-          color: colorScheme.outlineVariant.withOpacity(0.15),
+          color: context.appColors.ghostBorder,
         ),
       ),
       child: Column(
@@ -222,7 +215,7 @@ class GlassBottomSheet extends StatelessWidget {
             width: 40,
             height: 4,
             decoration: BoxDecoration(
-              color: colorScheme.outlineVariant.withOpacity(0.5),
+              color: context.colors.outlineVariant.withValues(alpha: 0.5),
               borderRadius: BorderRadius.circular(2),
             ),
           ),
@@ -244,7 +237,7 @@ class GlassBottomSheet extends StatelessWidget {
                         style: TextStyle(
                           fontSize: 18,
                           fontWeight: FontWeight.bold,
-                          color: colorScheme.onSurface,
+                          color: context.colors.onSurface,
                         ),
                       ),
                     ),
@@ -254,14 +247,14 @@ class GlassBottomSheet extends StatelessWidget {
                       child: Container(
                         padding: EdgeInsets.all(AppSpacing.sm),
                         decoration: BoxDecoration(
-                          color: colorScheme.outlineVariant
+                          color: context.colors.outlineVariant
                               .withOpacity(0.2),
                           shape: BoxShape.circle,
                         ),
                         child: Icon(
                           Icons.close,
                           size: 18,
-                          color: colorScheme.onSurfaceVariant,
+                          color: context.colors.onSurfaceVariant,
                         ),
                       ),
                     ),