feat(phase2e-2): 落地会议生命周期状态机 + Router 幂等双层防御（Task 8）

核心交付：
- 新建 MeetingLifecycleService（6 钩子 + sync.Map 本地 timer + Redis key 双保险 + RescheduleFromRedis）
- 新建 MeetingCleanupTask（启动重建 timer + 每 N 秒扫 host_grace/empty_ttl 兜底 + 4h stale active 回收）
- MediaOrchestrator 新增 ResolveRouterID；HTTPMediaOrchestrator.CreateRouter 入口 sync.Map 幂等防御
- 业务层 JoinRoom 移除 CreateRouter 调用改走 CancelEmptyTTL + ResolveRouterID；LeaveRoom 空房分支改调 OnAllMembersLeft 不再立即销毁
- MeetingSignalService 新增 OnWSDisconnect 实现 ws.MeetingDisconnectHook；OnRoomJoin 追加 host 重连钩子
- ws.handler 定义 MeetingDisconnectHook 接口 + SetMeetingDisconnectHook，解耦 ws→meeting 反向依赖
- config 新增 MeetingConfig{HostGrace=120, EmptyRoomTTL=300, CleanupInterval=30, StaleRoomHours=4}

关键设计决策：
- Redis key TTL = 业务时长 + max(CleanupIntervalSeconds*2, 30s) buffer：避免本地 timer 与
  Redis 自动过期同步到期导致 DEL 返回 0 被误判为"已被其他路径处理"而跳过业务逻辑
- Router 幂等双层防御（决策 q2_router_dedup=a2_both）：业务层不重复调 + HTTP 层 sync.Map 命中直接返回
- 普通成员 WS 断开仅清 media 资源不动 participant 表（决策 q1_nonhost_disconnect=a1_keep_current）

E2E 验证：docs/verify/meeting_t8_verify.mjs PASS=20 FAIL=0，覆盖 5 场景：
- S1 host 宽限期过期自动转让（meeting.host.changed + DB host_id 更新）
- S2 宽限期内重连保留身份
- S3 empty_ttl 期内新成员加入复活房间
- S4 empty_ttl 过期 → 房间 Ended + 新 join 被拒
- S5 CreateRoom +1 Router / JoinRoom 不再创建新 Router（通过 media-server /internal/info stats.routers 断言）

media-server：/internal/info 响应追加 stats.routers + routers[] 供 E2E 断言 Router 幂等

文档同步：
- docs/progress/CURRENT_STATUS.md 头部 + 新增 Task 8 交付条目
- docs/plans/2026-04-21-phase2e-2-implementation.plan.md Task 8 标记完成 + 实际产出/决策/验证
- docs/api/frontend/meeting.md 补充 host.changed.auto_reason / room.ended.reason=system_error / 空房 TTL 复活语义 + Task 8 验证记录
- docs/architecture/system-architecture.md meeting 模块职责补充"会议生命周期状态机"
- .cursor/rules/project-context.mdc 追加 Task 8 条目并更新 Phase 2e-2 进度（Task 0-8 ✅）

Made-with: Cursor

backend/go-service/app/provider/provider.go

@@ -13,6 +13,7 @@ import (
 	imHandler "github.com/echochat/backend/app/im/handler"
 	meetingController "github.com/echochat/backend/app/meeting/controller"
 	meetingService "github.com/echochat/backend/app/meeting/service"
+	meetingTask "github.com/echochat/backend/app/meeting/task"
 	notifyController "github.com/echochat/backend/app/notify/controller"
 	notifyService "github.com/echochat/backend/app/notify/service"
 	notifyTask "github.com/echochat/backend/app/notify/task"
@@ -56,8 +57,10 @@ type App struct {
 	NotifyCleanupTask     *notifyTask.CleanupTask                    // 通知清理定时任务
 	MeetingService        *meetingService.MeetingService             // 会议 REST 业务服务（Task 5 落地）
 	MeetingSignalService  *meetingService.MeetingSignalService       // 会议 WS 信令业务服务（Task 6 落地）
+	MeetingLifecycleSvc   *meetingService.MeetingLifecycleService    // 会议生命周期状态机（Task 8 落地）
 	MeetingController     *meetingController.MeetingController       // 会议 REST 控制器
 	MeetingWSHandler      *meetingController.MeetingWSHandler        // 会议 WS 事件 Handler（构造时自动注册路由到 Hub）
+	MeetingCleanupTask    *meetingTask.MeetingCleanupTask            // 会议生命周期兜底定时任务（Task 8 落地）
 }
 
 // NewApp 创建应用实例
@@ -89,11 +92,14 @@ func NewApp(
 	notifyCleanup *notifyTask.CleanupTask,
 	meetingSvc *meetingService.MeetingService,
 	meetingSignalSvc *meetingService.MeetingSignalService,
+	meetingLifecycleSvc *meetingService.MeetingLifecycleService,
 	meetingCtrl *meetingController.MeetingController,
 	meetingWSHandler *meetingController.MeetingWSHandler,
+	meetingCleanup *meetingTask.MeetingCleanupTask,
 ) *App {
 	wsHandler.SetOfflinePusher(offlinePusher)
 	wsHandler.SetNotifyConnectHook(notifySvc)
+	wsHandler.SetMeetingDisconnectHook(meetingSignalSvc)
 
 	return &App{
 		Config:                  cfg,
@@ -123,8 +129,10 @@ func NewApp(
 		NotifyCleanupTask:       notifyCleanup,
 		MeetingService:          meetingSvc,
 		MeetingSignalService:    meetingSignalSvc,
+		MeetingLifecycleSvc:     meetingLifecycleSvc,
 		MeetingController:       meetingCtrl,
 		MeetingWSHandler:        meetingWSHandler,
+		MeetingCleanupTask:      meetingCleanup,
 	}
 }
 

backend/go-service/app/provider/wire.go

@@ -54,6 +54,8 @@ func InitializeApp(cfg *config.Config) (*App, error) {
 		wire.Bind(new(meetingService.NotifyPusher), new(*notifyService.NotifyService)),
 		wire.Bind(new(meetingService.UserInfoResolver), new(*contactDAO.FriendshipDAO)),
 		wire.Bind(new(meetingService.OnlineChecker), new(*wsApp.OnlineService)),
+		// Task 8：WS 断线钩子 → MeetingSignalService
+		wire.Bind(new(wsApp.MeetingDisconnectHook), new(*meetingService.MeetingSignalService)),
 	)
 	return nil, nil
 }

backend/go-service/app/provider/wire_gen.go

@@ -25,6 +25,7 @@ import (
 	controller7 "github.com/echochat/backend/app/meeting/controller"
 	dao6 "github.com/echochat/backend/app/meeting/dao"
 	service7 "github.com/echochat/backend/app/meeting/service"
+	task2 "github.com/echochat/backend/app/meeting/task"
 	controller6 "github.com/echochat/backend/app/notify/controller"
 	dao5 "github.com/echochat/backend/app/notify/dao"
 	service3 "github.com/echochat/backend/app/notify/service"
@@ -103,10 +104,12 @@ func InitializeApp(cfg *config.Config) (*App, error) {
 	meetingChatDAO := dao6.NewMeetingChatDAO(gormDB)
 	meetingBroadcaster := service7.NewMeetingBroadcaster(meetingParticipantDAO, pubSub)
 	httpMediaOrchestrator := service7.NewHTTPMediaOrchestrator(cfg)
-	meetingService := service7.NewMeetingService(meetingRoomDAO, meetingParticipantDAO, meetingChatDAO, gormDB, client, meetingBroadcaster, notifyService, friendshipDAO, onlineService, httpMediaOrchestrator)
-	meetingSignalService := service7.NewMeetingSignalService(meetingRoomDAO, meetingParticipantDAO, client, meetingBroadcaster, httpMediaOrchestrator)
+	meetingLifecycleService := service7.NewMeetingLifecycleService(meetingRoomDAO, meetingParticipantDAO, client, meetingBroadcaster, httpMediaOrchestrator, cfg)
+	meetingService := service7.NewMeetingService(meetingRoomDAO, meetingParticipantDAO, meetingChatDAO, gormDB, client, meetingBroadcaster, notifyService, friendshipDAO, onlineService, httpMediaOrchestrator, meetingLifecycleService)
+	meetingSignalService := service7.NewMeetingSignalService(meetingRoomDAO, meetingParticipantDAO, client, meetingBroadcaster, httpMediaOrchestrator, meetingLifecycleService)
 	meetingController := controller7.NewMeetingController(meetingService)
 	meetingWSHandler := controller7.NewMeetingWSHandler(meetingSignalService, hub)
-	app := NewApp(cfg, gormDB, client, minioClient, authService, authController, adminAuthController, userManageController, onlineController, contactManageController, groupManageController, messageManageController, handler, hub, pubSub, onlineService, contactController, imController, eventHandler, offlinePusher, fileController, groupController, notifyService, notificationController, cleanupTask, meetingService, meetingSignalService, meetingController, meetingWSHandler)
+	meetingCleanupTask := task2.NewMeetingCleanupTask(meetingLifecycleService, meetingRoomDAO, meetingChatDAO)
+	app := NewApp(cfg, gormDB, client, minioClient, authService, authController, adminAuthController, userManageController, onlineController, contactManageController, groupManageController, messageManageController, handler, hub, pubSub, onlineService, contactController, imController, eventHandler, offlinePusher, fileController, groupController, notifyService, notificationController, cleanupTask, meetingService, meetingSignalService, meetingLifecycleService, meetingController, meetingWSHandler, meetingCleanupTask)
 	return app, nil
 }