fix: login persistence, username login, realtime refresh, group name uniqueness

- Fix cookie path to '/' for auth persistence across page refreshes
- Login field now accepts both username and email
- Add 30s polling for group list and team session status refresh
- Add group name uniqueness check before creation

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/views/Layout.vue

@@ -23,16 +23,28 @@ const showScheduleModal = ref(false)
 const showCreateGroup = ref(false)
 const showJoinGroup = ref(false)
 
+let refreshTimer: ReturnType<typeof setInterval> | null = null
+
 onMounted(async () => {
   await userStore.initUser()
   await groupStore.loadGroups()
   await teamStore.loadActiveSession()
   await notificationStore.loadPendingInvitations()
   await notificationStore.startListening()
+
+  // 每30秒轮询刷新群组列表和临时小组状态
+  refreshTimer = setInterval(async () => {
+    await groupStore.loadGroups()
+    await teamStore.loadActiveSession()
+  }, 30000)
 })
 
 onUnmounted(() => {
   notificationStore.stopListening()
+  if (refreshTimer) {
+    clearInterval(refreshTimer)
+    refreshTimer = null
+  }
 })
 
 function handleLogout() {