feat: 为划转页面切换按钮添加旋转动画

- 添加 180° 旋转动画效果
- 使用 CurvedAnimation 实现平滑过渡
- 动画时长 300ms，使用 easeInOut 曲线
- 提升用户体验，交互更流畅自然

flutter_monisuo/lib/ui/pages/asset/transfer_page.dart

@@ -18,14 +18,29 @@ class TransferPage extends StatefulWidget {
   State<TransferPage> createState() => _TransferPageState();
 }
 
-class _TransferPageState extends State<TransferPage> {
+class _TransferPageState extends State<TransferPage> with SingleTickerProviderStateMixin {
   final _amountController = TextEditingController();
   int _direction = 1; // 1: 资金→交易, 2: 交易→资金
   bool _isLoading = false;
+  late AnimationController _rotationController;
+  late Animation<double> _rotationAnimation;
 
   @override
   void initState() {
     super.initState();
+    // 初始化旋转动画
+    _rotationController = AnimationController(
+      duration: const Duration(milliseconds: 300),
+      vsync: this,
+    );
+    _rotationAnimation = Tween<double>(
+      begin: 0,
+      end: 0.5, // 180度 = 0.5 圈
+    ).animate(CurvedAnimation(
+      parent: _rotationController,
+      curve: Curves.easeInOut,
+    ));
+    
     WidgetsBinding.instance.addPostFrameCallback((_) {
       context.read<AssetProvider>().refreshAll(force: true);
     });
@@ -34,6 +49,7 @@ class _TransferPageState extends State<TransferPage> {
   @override
   void dispose() {
     _amountController.dispose();
+    _rotationController.dispose();
     super.dispose();
   }
 
@@ -128,6 +144,19 @@ class _TransferPageState extends State<TransferPage> {
     _amountController.text = amount.toStringAsFixed(8).replaceAll(RegExp(r'\.?0+$'), '');
   }
 
+  /// 切换方向并触发旋转动画
+  void _toggleDirection() {
+    setState(() {
+      _direction = _direction == 1 ? 2 : 1;
+    });
+    
+    // 触发旋转动画
+    if (_rotationController.status == AnimationStatus.completed) {
+      _rotationController.reset();
+    }
+    _rotationController.forward();
+  }
+
   @override
   Widget build(BuildContext context) {
     final colorScheme = Theme.of(context).colorScheme;
@@ -169,24 +198,27 @@ class _TransferPageState extends State<TransferPage> {
 
                 // 方向切换按钮
                 GestureDetector(
-                  onTap: () => setState(() => _direction = _direction == 1 ? 2 : 1),
-                  child: Container(
-                    margin: EdgeInsets.symmetric(vertical: AppSpacing.sm),
-                    padding: EdgeInsets.all(AppSpacing.sm + AppSpacing.xs),
-                    decoration: BoxDecoration(
-                      color: colorScheme.primary,
-                      shape: BoxShape.circle,
-                      boxShadow: [
-                        BoxShadow(
-                          color: colorScheme.primary.withOpacity(0.3),
-                          blurRadius: 8,
-                        ),
-                      ],
-                    ),
-                    child: Icon(
-                      Icons.swap_vert,
-                      color: colorScheme.onPrimary,
-                      size: 22,
+                  onTap: _toggleDirection,
+                  child: RotationTransition(
+                    turns: _rotationAnimation,
+                    child: Container(
+                      margin: EdgeInsets.symmetric(vertical: AppSpacing.sm),
+                      padding: EdgeInsets.all(AppSpacing.sm + AppSpacing.xs),
+                      decoration: BoxDecoration(
+                        color: colorScheme.primary,
+                        shape: BoxShape.circle,
+                        boxShadow: [
+                          BoxShadow(
+                            color: colorScheme.primary.withOpacity(0.3),
+                            blurRadius: 8,
+                          ),
+                        ],
+                      ),
+                      child: Icon(
+                        Icons.swap_vert,
+                        color: colorScheme.onPrimary,
+                        size: 22,
+                      ),
                     ),
                   ),
                 ),