fix(theme): 修复亮色模式绿色对比度不足问题

- 添加主题感知颜色函数: getUpColor/getUpBackgroundColor
- app_color_scheme: 新增 getBuyGradient/getEmeraldGradient
- asset_card: emeraldGradient 支持主题切换
- neon_glow: 按钮颜色主题感知
- home_page: 涨跌颜色动态适配
- asset_page: 资产涨跌颜色适配
- trade_page: 交易涨跌颜色适配
- mine_page: 我的页面颜色适配

修复: 亮色模式下绿色 (#00a878) 与浅色背景对比度不足
效果: 亮色模式使用深绿色，深色模式使用亮绿色

flutter_monisuo/lib/ui/components/asset_card.dart

@@ -30,9 +30,11 @@ class AssetCard extends StatelessWidget {
     end: Alignment.bottomRight,
   );
 
-  /// 翡翠渐变 - 用于盈利展示
-  static const emeraldGradient = LinearGradient(
-    colors: [AppColorScheme.darkTertiary, Color(0xFF7de8b8)],
+  /// 翡翠渐变 - 用于盈利展示（主题感知）
+  static LinearGradient getEmeraldGradient(bool isDark) => LinearGradient(
+    colors: isDark
+        ? [AppColorScheme.darkTertiary, const Color(0xFF7de8b8)]
+        : [AppColorScheme.lightTertiary, const Color(0xFF00c987)],
     begin: Alignment.topLeft,
     end: Alignment.bottomRight,
   );

flutter_monisuo/lib/ui/components/neon_glow.dart

@@ -214,7 +214,7 @@ class _NeonButtonState extends State<NeonButton>
       case NeonButtonType.secondary:
         return colorScheme.secondary;
       case NeonButtonType.tertiary:
-        return AppColorScheme.up;
+        return AppColorScheme.getUpColor(isDark);
       case NeonButtonType.error:
         return AppColorScheme.down;
       case NeonButtonType.outline:
@@ -250,7 +250,7 @@ class _NeonButtonState extends State<NeonButton>
       case NeonButtonType.secondary:
         return colorScheme.secondary.withOpacity(isDark ? 0.15 : 0.08);
       case NeonButtonType.tertiary:
-        return AppColorScheme.up.withOpacity(isDark ? 0.2 : 0.1);
+        return AppColorScheme.getUpBackgroundColor(isDark, opacity: isDark ? 0.2 : 0.1);
       case NeonButtonType.error:
         return AppColorScheme.down.withOpacity(0.3);
       case NeonButtonType.outline:
@@ -278,7 +278,7 @@ class _NeonButtonState extends State<NeonButton>
           end: const Alignment(0.7, 0.7),
         );
       case NeonButtonType.tertiary:
-        return AppColorScheme.buyGradient;
+        return AppColorScheme.getBuyGradient(isDark);
       case NeonButtonType.error:
         return AppColorScheme.sellGradient;
       default: