rtc: report participant session end time on room move (#4561)

MoveToRoom resets the participant reporter resolver to receive new
(room, participant_session) keys for the destination, but the source
room's participant_session row never gets an end_time — the periodic
duration scrape only emits one once disconnectedAt is set, and a move
doesn't transition the participant to DISCONNECTED. Report end_time
immediately before the reset so the row is closed out cleanly.

pkg/rtc/participant.go

@@ -4069,6 +4069,7 @@ func (p *ParticipantImpl) MoveToRoom(params types.MoveToRoomParams) {
 	p.telemetryGuard = &telemetry.ReferenceGuard{}
 	p.lock.Unlock()
 
+	p.params.Reporter.ReportEndTime(time.Now())
 	p.params.LoggerResolver.Reset()
 	p.params.ReporterResolver.Reset()
 	p.setListener(params.Listener)