feat: 添加安全仪表板前端页面

- 新增 SecurityPage.vue: 统计卡片、威胁事件表格、封禁管理、风险查询
- 新增 api/security.js: 安全相关API封装
- 路由添加 /security 页面
- 侧边栏添加"安全防护"菜单项

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

admin-frontend/src/router/index.js

@@ -8,6 +8,7 @@ const FeedbacksPage = () => import('../pages/FeedbacksPage.vue')
 const LogsPage = () => import('../pages/LogsPage.vue')
 const AnnouncementsPage = () => import('../pages/AnnouncementsPage.vue')
 const EmailPage = () => import('../pages/EmailPage.vue')
+const SecurityPage = () => import('../pages/SecurityPage.vue')
 const SystemPage = () => import('../pages/SystemPage.vue')
 const SettingsPage = () => import('../pages/SettingsPage.vue')
 
@@ -25,6 +26,7 @@ const routes = [
       { path: '/logs', name: 'logs', component: LogsPage },
       { path: '/announcements', name: 'announcements', component: AnnouncementsPage },
       { path: '/email', name: 'email', component: EmailPage },
+      { path: '/security', name: 'security', component: SecurityPage },
       { path: '/system', name: 'system', component: SystemPage },
       { path: '/settings', name: 'settings', component: SettingsPage },
     ],