feat(ui): 优化组件样式并添加现代弹窗模板

- 更新 trade_button.dart 使用新颜色系统
- 更新 coin_card.dart 使用新颜色系统
- 更新 asset_card.dart 使用新颜色系统
- 创建 modern_dialog.dart 现代弹窗模板
- 创建 modern_bottom_sheet.dart 现代底部抽屉模板

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

flutter_monisuo/lib/ui/components/trade_button.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:shadcn_ui/shadcn_ui.dart';
+import '../../core/theme/app_color_scheme.dart';
 
 /// 交易按钮组件 - 买入/卖出按钮
 class TradeButton extends StatelessWidget {
@@ -9,10 +10,6 @@ class TradeButton extends StatelessWidget {
   final bool isLoading;
   final bool fullWidth;
 
-  // 颜色常量
-  static const buyColor = Color(0xFF00C853);
-  static const sellColor = Color(0xFFFF5252);
-
   const TradeButton({
     super.key,
     this.isBuy = true,
@@ -42,7 +39,7 @@ class TradeButton extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final color = isBuy ? buyColor : sellColor;
+    final color = isBuy ? AppColorScheme.up : AppColorScheme.down;
     final text = isBuy ? '买入${coinCode != null ? ' $coinCode' : ''}' : '卖出${coinCode != null ? ' $coinCode' : ''}';
     final icon = isBuy ? LucideIcons.arrowDownToLine : LucideIcons.arrowUpFromLine;