fix(theme): 修复组件主题硬编码问题

- asset_card: Colors.white/black → colorScheme
- gradient_button: Colors.white → onPrimary
- trade_button: Colors.white → onPrimary
- 支持亮/暗主题动态切换

flutter_monisuo/lib/ui/components/asset_card.dart

@@ -52,9 +52,14 @@ class AssetCard extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     final theme = ShadTheme.of(context);
+    final colorScheme = Theme.of(context).colorScheme;
     final isDark = Theme.of(context).brightness == Brightness.dark;
     final cardGradient = gradient ?? defaultGradientBuilder(isDark);
 
+    // 主题感知颜色 - 在渐变背景上使用 onPrimary
+    final primaryTextColor = colorScheme.onPrimary;
+    final secondaryTextColor = colorScheme.onPrimary.withValues(alpha: 0.7);
+
     return GestureDetector(
       onTap: onTap,
       child: Container(
@@ -65,7 +70,7 @@ class AssetCard extends StatelessWidget {
           borderRadius: BorderRadius.circular(AppRadius.xl),
           boxShadow: [
             BoxShadow(
-              color: Colors.black.withValues(alpha: 0.1),
+              color: colorScheme.onSurface.withValues(alpha: 0.1),
               blurRadius: 10,
               offset: const Offset(0, 4),
             ),
@@ -79,13 +84,13 @@ class AssetCard extends StatelessWidget {
               children: [
                 Text(
                   title,
-                  style: theme.textTheme.small.copyWith(color: Colors.white70),
+                  style: theme.textTheme.small.copyWith(color: secondaryTextColor),
                 ),
                 const Spacer(),
                 if (onTap != null)
-                  const Icon(
+                  Icon(
                     LucideIcons.chevronRight,
-                    color: Colors.white70,
+                    color: secondaryTextColor,
                     size: 18,
                   ),
               ],
@@ -96,7 +101,7 @@ class AssetCard extends StatelessWidget {
               balance,
               style: theme.textTheme.h1.copyWith(
                 fontWeight: FontWeight.bold,
-                color: Colors.white,
+                color: primaryTextColor,
                 fontSize: 32,
               ),
             ),
@@ -107,13 +112,13 @@ class AssetCard extends StatelessWidget {
                 children: [
                   Icon(
                     isProfit == true ? LucideIcons.trendingUp : LucideIcons.trendingDown,
-                    color: Colors.white70,
+                    color: secondaryTextColor,
                     size: 16,
                   ),
                   const SizedBox(width: 6),
                   Text(
                     '盈亏: $profit',
-                    style: theme.textTheme.small.copyWith(color: Colors.white70),
+                    style: theme.textTheme.small.copyWith(color: secondaryTextColor),
                   ),
                 ],
               ),
@@ -123,7 +128,7 @@ class AssetCard extends StatelessWidget {
               const SizedBox(height: AppSpacing.lg),
               Row(
                 mainAxisAlignment: MainAxisAlignment.spaceBetween,
-                children: items!.map((item) => _buildItem(item)).toList(),
+                children: items!.map((item) => _buildItem(item, primaryTextColor, secondaryTextColor)).toList(),
               ),
             ],
           ],
@@ -132,21 +137,21 @@ class AssetCard extends StatelessWidget {
     ).animate().fadeIn(duration: 400.ms).slideY(begin: 0.1, end: 0);
   }
 
-  Widget _buildItem(AssetItem item) {
+  Widget _buildItem(AssetItem item, Color primaryTextColor, Color secondaryTextColor) {
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
         Text(
           item.label,
-          style: const TextStyle(fontSize: 12, color: Colors.white70),
+          style: TextStyle(fontSize: 12, color: secondaryTextColor),
         ),
         const SizedBox(height: 4),
         Text(
           item.value,
-          style: const TextStyle(
+          style: TextStyle(
             fontSize: 18,
             fontWeight: FontWeight.w600,
-            color: Colors.white,
+            color: primaryTextColor,
           ),
         ),
       ],