refactor: mock清理+安全配置+通用组件+菜单优化

P0安全: SECRET_KEY/ADMIN_PASSWORD/CORS环境变量化, seed仅admin

P1Mock: mock.ts 301->88行, 删8数据mock+5generateMock, net-1300行

P2组件: useToast/useFetchList+ConfirmDialog/FormDialog

P3菜单: menuSections/menuItems->constants/menu.ts

P4API: NotificationsPage/WorkflowPage重写+RolesPage演示

测试: 1050passed, tsc clean

frontend/src/pages/SettingsPage.tsx

@@ -1,10 +1,12 @@
 import { useState } from 'react';
+import PlatformConfigPage from './PlatformConfigPage';
+import AuditRulesPage from './AuditRulesPage';
 import AnnouncementPage from './AnnouncementPage';
 import NotificationPage from './NotificationPage';
 import LdapConfigPage from './LdapConfigPage';
-import AuditRulesPage from './AuditRulesPage';
 
 const tabs = [
+  { id: 'platform', label: '平台配置', icon: '⚙️' },
   { id: 'rules', label: '审核规则', icon: '🛡️' },
   { id: 'announcement', label: '公告管理', icon: '📢' },
   { id: 'notification', label: '消息推送', icon: '🔔' },
@@ -14,7 +16,7 @@ const tabs = [
 type TabId = typeof tabs[number]['id'];
 
 export default function SettingsPage() {
-  const [activeTab, setActiveTab] = useState<TabId>('rules');
+  const [activeTab, setActiveTab] = useState<TabId>('platform');
 
   return (
     <div className="space-y-5">
@@ -43,6 +45,7 @@ export default function SettingsPage() {
 
       {/* 内容区 */}
       <div>
+        {activeTab === 'platform' && <PlatformConfigPage />}
         {activeTab === 'rules' && <AuditRulesPage />}
         {activeTab === 'announcement' && <AnnouncementPage />}
         {activeTab === 'notification' && <NotificationPage />}