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

backend/app/api/v1/router.py

@@ -7,6 +7,7 @@ from app.api.v1.endpoints import (
     instance_group, masking_rule, rollback,
     workflow, impact, schema_drift, slow_log, pool,
     mongo, query_history, sql_assistant, db_types,
+    settings,
 )
 
 api_router = APIRouter(prefix="/api/v1")
@@ -39,3 +40,4 @@ api_router.include_router(query_history.router)
 api_router.include_router(sql_assistant.router)
 
 api_router.include_router(db_types.router)
+api_router.include_router(settings.router, prefix="/settings", tags=["系统设置"])