fix: member status visibility, team creation improvements, join approval flow

- Fix other members' status not visible due to users collection viewRule restriction
- Fix empty status treated as 'away' instead of 'idle' in membersByStatus
- Auto-set creator to 'in_team' status when creating team session
- Filter current user from idle members invite list
- Fix group store isGroupOwner using pb.authStore instead of localStorage
- Add nginx no-cache headers for index.html
- Add join_requests collection migration and join approval flow
- Update groups collection rules and add requireApproval field
- Add Memory types for Phase 2 planning

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

frontend/src/stores/group.ts

@@ -2,6 +2,7 @@
 import { defineStore } from 'pinia'
 import { ref, computed } from 'vue'
 import type { Group, User } from '@/types'
+import { pb } from '@/api/pocketbase'
 import { getUserGroups, getGroup, getGroupMembers } from '@/api/groups'
 
 export const useGroupStore = defineStore('group', () => {
@@ -14,8 +15,7 @@ export const useGroupStore = defineStore('group', () => {
   // 计算属性
   const currentGroupId = computed(() => currentGroup.value?.id || '')
   const isGroupOwner = computed(() => {
-    const userId = localStorage.getItem('userId')
-    return currentGroup.value?.owner === userId
+    return currentGroup.value?.owner === pb.authStore.model?.id
   })
 
   // 加载用户的群组列表