fix(admin-web): snapshots 页面补上 PageContainer 包裹，恢复侧边栏

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

frontend/admin-web/src/app/(dashboard)/snapshots/page.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useEffect, useCallback } from 'react';
+import { PageContainer } from '@/components/layout';
 import { snapshotApi } from '@/infrastructure/api/snapshot.api';
 import { useSnapshotPolling } from '@/hooks/useSnapshotPolling';
 import type {
@@ -166,8 +167,8 @@ export default function SnapshotsPage() {
   };
 
   return (
-    <div className={styles.container}>
-      <h1 className={styles.title}>数据快照</h1>
+    <PageContainer title="数据快照">
+      <div className={styles.container}>
 
       {/* 创建备份表单 */}
       <div className={styles.card}>
@@ -348,6 +349,7 @@ export default function SnapshotsPage() {
           </div>
         )}
       </div>
-    </div>
+      </div>
+    </PageContainer>
   );
 }