task-55(账号/权限页面): 实现菜单新增表单

menu-manage-model.ts 增 createMenuForm/flattenMenuNodes/nextSiblingSort；menu-manage-api.ts
增 createMenu POST /api/admin/permission-menus(unwrap+解析落库节点)；MenusPage 新增菜单
Dialog(名称/标识/父菜单/路由/排序)校验后提交并刷新。8 用例全过，403 单测 + build 绿。

admin-frontend-vue/src/pages/account/menu-manage-api.ts

@@ -1,9 +1,13 @@
 /** 菜单管理列表加载适配（任务 54）：GET /api/admin/permission-menus(admin) → 展示树。 */
 import { http } from '@/api/http'
+import { unwrap } from '@/api/envelope'
 import {
   ADMIN_MENU_TYPE,
   buildMenuManageTree,
+  parseMenuManageItem,
   parseMenuManageList,
+  toMenuCreateRequest,
+  type MenuManageForm,
   type MenuManageNode,
 } from './menu-manage-model'
 
@@ -19,3 +23,11 @@ export async function fetchMenuManageNodes(): Promise<MenuManageNode[]> {
 export async function loadMenuManageTree(): Promise<MenuManageNode[]> {
   return buildMenuManageTree(await fetchMenuManageNodes())
 }
+
+/** 新建菜单：POST /api/admin/permission-menus，返回后端落库节点。 */
+export async function createMenu(form: MenuManageForm): Promise<MenuManageNode> {
+  const { data } = await http.post<unknown>(MENUS_ENDPOINT, toMenuCreateRequest(form))
+  const created = parseMenuManageItem(unwrap<unknown>(data))
+  if (!created) throw new Error('创建菜单响应异常：缺少菜单数据')
+  return created
+}