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>

docs/plans/2026-04-17-game-group-v2-design.md

@@ -159,6 +159,19 @@ NAS 服务器
   icon: string
   awardedAt: date
 }
+
+// memories - 多媒体记忆（音视频等）
+{
+  id: string
+  groupId: string
+  uploader: string (userId)
+  title: string
+  description: string
+  file: string (PocketBase file field)
+  fileType: "image" | "video" | "audio" | "other"
+  size: number (bytes)
+  createdAt: date
+}
 ```
 
 ### 3.3 三期数据集合
@@ -398,11 +411,12 @@ NAS 服务器
 
 ### 第二期
 
-**目标**: 预约 + 积分 + 荣誉
+**目标**: 预约 + 积分 + 荣誉 + 记忆
 
 - [ ] 预约系统（简化投票）
 - [ ] 积分系统（获取/记录）
 - [ ] 荣誉墙（自动授予）
+- [ ] 多媒体记忆（支持音视频等多媒体文件的上传、下载与在线预览）
 
 ### 第三期