task-26(会话/菜单/权限): 实现 401 登录跳转行为防循环守卫

401 统一跳 /login 并携带目标路径；新增纯函数守卫 isLoginLocation/
isAuthEndpointRequest/shouldRedirectUnauthorized：已处登录页或失败请求即
登录端点时不再二次跳转，避免登录页死循环与吞掉登录失败反馈。http 层
success/error 两支均带失败请求 URL 过守卫后再跳转。envelope/http 单测
8 用例 + 全量 179 单测 + vue-tsc/vite build 通过。

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

@@ -1,5 +1,5 @@
 import axios from 'axios'
-import { isUnauthorized, loginRedirectTarget } from './envelope'
+import { isUnauthorized, loginRedirectTarget, shouldRedirectUnauthorized } from './envelope'
 
 export { unwrap } from './envelope'
 
@@ -9,8 +9,10 @@ export const http = axios.create({
   timeout: 30_000,
 })
 
-function redirectToLogin(): void {
+function redirectToLogin(requestUrl?: string): void {
   if (typeof window === 'undefined') return
+  // 已在登录页或失败请求即登录端点时不再跳转，避免登录页循环与吞掉登录失败反馈。
+  if (!shouldRedirectUnauthorized(window.location.pathname, requestUrl)) return
   const target = loginRedirectTarget(window.location)
   window.location.assign(`/login?redirect=${target}`)
 }
@@ -18,11 +20,13 @@ function redirectToLogin(): void {
 http.interceptors.response.use(
   (response) => {
     // Java 未登录以 HTTP 200 + body.code=401 返回，需统一按未登录处理。
-    if (isUnauthorized(response.data)) redirectToLogin()
+    if (isUnauthorized(response.data)) redirectToLogin(response.config?.url)
     return response
   },
   (error) => {
-    if (error?.response?.status === 401 || isUnauthorized(error?.response?.data)) redirectToLogin()
+    if (error?.response?.status === 401 || isUnauthorized(error?.response?.data)) {
+      redirectToLogin(error?.config?.url)
+    }
     return Promise.reject(error)
   },
 )