task-23(会话/菜单/权限): 实现当前用户请求适配 + 真后端 live 测试

session-model.parseCurrentUser 兼容 data:{item}/{item}/直接对象信封并校验 id；
session.ts fetchCurrentUser 复用；启用 allowImportingTsExtensions；npm run test:live
用 admin 账号真实登录打 18080 验证 current-user 与菜单树(023/024 live 全绿)。

admin-frontend-vue/src/api/session.ts

@@ -0,0 +1,19 @@
+import { http } from './http'
+import { parseCurrentUser, parseMenuTree } from './session-model'
+import type { AdminMenuNode, AdminUser, ApiEnvelope } from '../types/admin'
+
+export async function fetchCurrentUser(): Promise<AdminUser> {
+  const { data } = await http.get<ApiEnvelope<{ item: AdminUser }> | AdminUser>('/api/admin/current-user')
+  return parseCurrentUser(data)
+}
+
+export async function fetchAdminMenuTree(): Promise<AdminMenuNode[]> {
+  const { data } = await http.get<
+    ApiEnvelope<{ items: AdminMenuNode[] }> | { items: AdminMenuNode[] } | AdminMenuNode[]
+  >('/api/admin/current-user/menus')
+  return parseMenuTree(data)
+}
+
+export async function logout(): Promise<void> {
+  await http.post('/api/admin/logout', undefined, { headers: { 'X-Requested-With': 'XMLHttpRequest' } })
+}