解决登录回环问题

frontend/src/api/axios.ts

@@ -1,10 +1,13 @@
 import axios, { AxiosError, AxiosInstance, AxiosRequestConfig, AxiosResponse } from "axios";
 import { ElMessage } from "element-plus";
 import router from "../router";
-import { getToken, clearToken } from "../utils/auth";
+import { getToken } from "../utils/auth";
+import { useAuthStore } from "../store/auth";
 import type { ApiError } from "../types/api";
 import { useStudyStore } from "../store/study";
 
+let unauthorizedNotified = false;
+
 const instance: AxiosInstance = axios.create({
   baseURL: "/",
   timeout: 15000,
@@ -24,6 +27,19 @@ instance.interceptors.response.use(
   async (error: AxiosError<ApiError>) => {
     const status = error.response?.status;
     const data = error.response?.data;
+    // 401 统一处理：同步清理本地 token，并防止重复弹窗
+    const handleUnauthorized = () => {
+      const auth = useAuthStore();
+      auth.logout();
+      if (!unauthorizedNotified) {
+        unauthorizedNotified = true;
+        ElMessage.error(data?.message || "登录已过期，请重新登录");
+        setTimeout(() => {
+          unauthorizedNotified = false;
+        }, 1000);
+      }
+      router.push("/login");
+    };
     // 如果当前项目不存在或已失效，清理项目并跳到项目列表
     if (status === 404 && typeof data?.message === "string" && data.message.toLowerCase().includes("study")) {
       try {
@@ -35,9 +51,7 @@ instance.interceptors.response.use(
       router.push("/studies");
     }
     if (status === 401) {
-      clearToken();
-      ElMessage.error(data?.message || "登录已过期，请重新登录");
-      router.push("/login");
+      handleUnauthorized();
     } else if (data?.message) {
       ElMessage.error(data.message);
     } else {

frontend/src/router/index.ts

@@ -242,7 +242,8 @@ router.beforeEach(async (to, _from, next) => {
     try {
       await auth.fetchMe();
     } catch {
-      /* ignore */
+      // token 失效或用户不可用时立即登出，避免重复 401
+      auth.logout();
     }
   }
   if (!to.meta.public && !token) {