security(auth): P1 Token Refresh + sessionStorage

- 新增三個 refresh 端點（member/provider/admin），revoke 舊 token 發行新 7 天 token
- axios.js / coachAxios.js：401 interceptor 改為 refresh-then-retry，含 isRefreshing queue 防並發、isRedirecting flag 防雙重 redirect
- auth.js / coachAuth.js / AuthCallbackView.vue：localStorage 全改為 sessionStorage
- echo.js / notificationAxios.js：同步改為 sessionStorage
- notifications.js：401 時停止 polling（stopPolling），不印 error log
- 新增 TokenRefreshTest.php（11 tests / 24 assertions）：refresh 成功/失效/跨角色 403

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/axios.js

@@ -6,26 +6,75 @@ const api = axios.create({
 })
 
 api.interceptors.request.use((config) => {
-  const token = localStorage.getItem('token')
+  const token = sessionStorage.getItem('token')
   if (token) {
     config.headers.Authorization = `Bearer ${token}`
   }
   return config
 })
 
+let isRefreshing   = false
+let isRedirecting  = false
+let pendingRequests = []
+
+function resolvePending(token) {
+  pendingRequests.forEach((cb) => cb(token))
+  pendingRequests = []
+}
+
+function rejectPending(error) {
+  pendingRequests.forEach((cb) => cb(null, error))
+  pendingRequests = []
+}
+
 api.interceptors.response.use(
   (response) => response,
-  (error) => {
-    if (
-      error.response?.status === 401 &&
-      !error.config.url.includes('/login') &&
-      !error.config.url.includes('/register')
-    ) {
-      localStorage.removeItem('token')
-      localStorage.removeItem('user')
-      window.location.href = '/login'
+  async (error) => {
+    const config = error.config
+    const status = error.response?.status
+
+    const isAuthEndpoint =
+      config.url.includes('/login') ||
+      config.url.includes('/register') ||
+      config.url.includes('/refresh')
+
+    if (status !== 401 || isAuthEndpoint || config._retry) {
+      return Promise.reject(error)
+    }
+
+    if (isRefreshing) {
+      return new Promise((resolve, reject) => {
+        pendingRequests.push((token, err) => {
+          if (err) return reject(err)
+          config.headers.Authorization = `Bearer ${token}`
+          resolve(api(config))
+        })
+      })
+    }
+
+    config._retry = true
+    isRefreshing = true
+
+    try {
+      const { data } = await api.post('/member/refresh')
+      const newToken = data.data.token
+      sessionStorage.setItem('token', newToken)
+      api.defaults.headers.common['Authorization'] = `Bearer ${newToken}`
+      resolvePending(newToken)
+      config.headers.Authorization = `Bearer ${newToken}`
+      return api(config)
+    } catch {
+      rejectPending(error)
+      if (!isRedirecting) {
+        isRedirecting = true
+        sessionStorage.removeItem('token')
+        sessionStorage.removeItem('user')
+        window.location.href = '/login'
+      }
+      return Promise.reject(error)
+    } finally {
+      isRefreshing = false
     }
-    return Promise.reject(error)
   }
 )