fix: 修复划转页面卡片互换动画效果

- 重写 AnimatedSwitcher 实现，移除多余的 Container 包裹
- 直接在 _buildAccountCard 上设置 ValueKey
- 使用 SlideTransition + FadeTransition 组合
- 上方卡片从上滑入，下方卡片从下滑入
- 动画时长 300ms，easeInOut 曲线
- 动画效果更流畅自然，卡片互换位置清晰可见

flutter_monisuo/build/web/flutter_bootstrap.js

@@ -37,6 +37,6 @@ _flutter.buildConfig = {"engineRevision":"e4b8dca3f1b4ede4c30371002441c88c12187e
 
 _flutter.loader.load({
   serviceWorkerSettings: {
-    serviceWorkerVersion: "3656927942" /* Flutter's service worker is deprecated and will be removed in a future Flutter release. */
+    serviceWorkerVersion: "2359170310" /* Flutter's service worker is deprecated and will be removed in a future Flutter release. */
   }
 });