feat: 优化交易账户和币种选择功能

- 交易账户卡片添加总市值显示和持仓列表
- 持仓列表USDT自动排在最上面
- 交易页面添加币种选择弹窗功能
- 行情页面点击币种跳转到交易页面
- 支持从外部传入选中币种参数

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

flutter_monisuo/lib/ui/pages/main/main_page.dart

@@ -14,9 +14,8 @@ import '../mine/mine_page.dart';
 class _NavItem {
   final String label;
   final IconData icon;
-  final Widget page;
 
-  const _NavItem({required this.label, required this.icon, required this.page});
+  const _NavItem({required this.label, required this.icon});
 }
 
 /// 主页面 - "The Kinetic Vault" 设计风格
@@ -24,20 +23,26 @@ class MainPage extends StatefulWidget {
   const MainPage({super.key});
 
   @override
-  State<MainPage> createState() => _MainPageState();
+  State<MainPage> createState() => MainPageState();
 }
 
-class _MainPageState extends State<MainPage> {
+class MainPageState extends State<MainPage> {
   int _currentIndex = 0;
   final Set<int> _loadedPages = {0};
+  String? _tradeCoinCode; // 交易页面选中的币种代码
+  late final List<Widget> _pages;
 
-  static final _navItems = [
-    _NavItem(label: '首页', icon: LucideIcons.house, page: const HomePage()),
-    _NavItem(label: '行情', icon: LucideIcons.trendingUp, page: const MarketPage()),
-    _NavItem(label: '交易', icon: LucideIcons.arrowLeftRight, page: const TradePage()),
-    _NavItem(label: '资产', icon: LucideIcons.wallet, page: const AssetPage()),
-    _NavItem(label: '我的', icon: LucideIcons.user, page: const MinePage()),
-  ];
+  @override
+  void initState() {
+    super.initState();
+    _pages = [
+      const HomePage(),
+      const MarketPage(),
+      TradePage(initialCoinCode: _tradeCoinCode),
+      const AssetPage(),
+      const MinePage(),
+    ];
+  }
 
   void _onTabChanged(int index) {
     setState(() {
@@ -46,6 +51,25 @@ class _MainPageState extends State<MainPage> {
     });
   }
 
+  /// 切换到交易页面并选中指定币种
+  void switchToTrade(String coinCode) {
+    setState(() {
+      _tradeCoinCode = coinCode;
+      _currentIndex = 2; // 交易页面索引
+      _loadedPages.add(2);
+      // 重新构建交易页面
+      _pages[2] = TradePage(initialCoinCode: _tradeCoinCode);
+    });
+  }
+
+  static const _navItems = [
+    _NavItem(label: '首页', icon: LucideIcons.house),
+    _NavItem(label: '行情', icon: LucideIcons.trendingUp),
+    _NavItem(label: '交易', icon: LucideIcons.arrowLeftRight),
+    _NavItem(label: '资产', icon: LucideIcons.wallet),
+    _NavItem(label: '我的', icon: LucideIcons.user),
+  ];
+
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
@@ -61,7 +85,7 @@ class _MainPageState extends State<MainPage> {
             child: LazyIndexedStack(
               index: _currentIndex,
               loadedIndexes: _loadedPages,
-              children: _navItems.map((item) => item.page).toList(),
+              children: _pages,
             ),
           ),
         ],