feat: 个人微信改为前台每用户独立绑定(按 user_id 隔离)，后台仅保留全局 Bot

frontend/src/components/layout/FrontLayout.tsx

@@ -12,6 +12,7 @@ const navItems = [
   { path: '/pricing', icon: 'pricing', label: '付费中心' },
   { path: '/assets', icon: 'assets', label: '资产文件' },
   { path: '/evolution', icon: 'evolution', label: 'AI自进化' },
+  { path: '/wechat-bot', icon: 'wechat', label: '微信机器人' },
 ];
 
 const bottomItems = [
@@ -31,6 +32,7 @@ const iconPaths: Record<string, JSX.Element> = {
   notify: <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round"><path d="M18 8A6 6 0 0 0 6 8c0 7-3 9-3 9h18s-3-2-3-9"/><path d="M13.73 21a2 2 0 0 1-3.46 0"/></svg>,
   assets: <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round"><path d="M13 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V9z"/><polyline points="13 2 13 9 20 9"/></svg>,
   evolution: <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round"><polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/></svg>,
+  wechat: <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round"><path d="M21 11.5a8.38 8.38 0 0 1-.9 3.8 8.5 8.5 0 0 1-7.6 4.7 8.38 8.38 0 0 1-3.8-.9L3 21l1.9-5.7a8.38 8.38 0 0 1-.9-3.8 8.5 8.5 0 0 1 4.7-7.6 8.38 8.38 0 0 1 3.8-.9h.5a8.48 8.48 0 0 1 8 8v.5z"/><circle cx="9" cy="11" r="1"/><circle cx="15" cy="11" r="1"/></svg>,
 };
 
 const FrontLayout: React.FC = () => {