后台前端：新增“监控审计”一级目录 (#63)

## 变更
- 左侧导航新增一级目录“监控审计”。
- 将设备存活、埋点成功率、埋点日志和审计日志统一迁入该目录。
- 从“看板”移除技术监控项，并取消埋点日志、审计日志的独立一级入口。
- 保留现有页面权限过滤逻辑：无可见子项时不会展示该目录。

## 验证
- `npm run build` 通过，Next.js 编译、lint 和 TypeScript 检查均成功。

## 后端配套
- WonderableAI/shaguabijia-app-server#159

---------

Co-authored-by: linkeyu <798648091@qq.com>
Reviewed-on: #63
Co-authored-by: linkeyu <linkeyu@wonderable.ai>
Co-committed-by: linkeyu <linkeyu@wonderable.ai>

src/app/(main)/layout.tsx

@@ -67,8 +67,6 @@ const NAV_GROUPS: NavGroup[] = [
       { key: '/comparison-records', icon: <ProfileOutlined />, label: '比价记录' },
       { key: '/coupon-data', icon: <GiftOutlined />, label: '领券记录' },
       { key: '/cps', icon: <ShareAltOutlined />, label: 'CPS收益' },
-      { key: '/device-liveness', icon: <HeartOutlined />, label: '设备存活' },
-      { key: '/analytics-health', icon: <LineChartOutlined />, label: '埋点成功率' },
     ],
   },
   {
@@ -92,9 +90,18 @@ const NAV_GROUPS: NavGroup[] = [
       { key: '/users', icon: <UserOutlined />, label: '用户管理' },
     ],
   },
+  {
+    key: 'monitoring-audit',
+    icon: <FileSearchOutlined />,
+    label: '监控审计',
+    children: [
+      { key: '/device-liveness', icon: <HeartOutlined />, label: '设备存活' },
+      { key: '/analytics-health', icon: <LineChartOutlined />, label: '埋点成功率' },
+      { key: '/event-logs', icon: <DatabaseOutlined />, label: '埋点日志' },
+      { key: '/audit-logs', icon: <FileSearchOutlined />, label: '审计日志' },
+    ],
+  },
   { key: '/admins', icon: <TeamOutlined />, label: '权限管理' },
-  { key: '/event-logs', icon: <DatabaseOutlined />, label: '埋点日志' },
-  { key: '/audit-logs', icon: <FileSearchOutlined />, label: '审计日志' },
 ];
 
 // 导航项 key(/dashboard)→ 权限页 key(dashboard),与后端 permissions.py 目录对齐