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/components/Layout.tsx

@@ -4,7 +4,7 @@ import {
   ClipboardList, Search, UserCog, Users, Lock, Shield, GitBranch, Bell,
   LogOut, Settings, Clock, Megaphone, Sun, Moon, BookOpen
 } from 'lucide-react';
-import { menuSections } from '@/lib/mock';
+import { menuSections } from '@/constants/menu';
 import { useAuth } from '@/hooks/useAuth';
 import { useTheme } from '@/hooks/useTheme';