audit fixes: align all frontend timestamps to Beijing time + debounce MarketPage search (vv2026.07.20.1)

frontend/src/pages/admin/Ads.tsx

@@ -1,6 +1,7 @@
 import React, { useState, useEffect } from 'react';
 import { adminAPI, marketAPI } from '@/api';
 import type { AdBanner, MarketApp } from '@/types';
+import { formatBjDate } from '@/utils/datetime';
 import './Ads.css';
 
 const SVGIcon: React.FC<{ children: React.ReactNode; size?: number }> = ({ children, size = 16 }) => (
@@ -281,7 +282,7 @@ const Ads: React.FC = () => {
                       </span>
                     </td>
                     <td style={{ fontSize: 'var(--text-xs)', color: 'var(--color-text-tertiary)' }}>
-                      {new Date(banner.createdAt).toLocaleDateString()}
+                      {formatBjDate(banner.createdAt)}
                     </td>
                     <td>
                       <div style={{ display: 'flex', gap: 'var(--space-xs)' }}>