[task] roominfo 나가기 (component)

### ISSUE
- Group: `client`
-Type: `feature`
-Detail: exit room(mogakco)

### TODO
1. [ ] 관련 db에서 해당 유저 삭제 및 roomlist로 이동
2. [ ] 방장이 나갈 경우 남아 있는 사람들에게 선착순으로 방장 권한 부여
3. [ ] 혼자 남았을 경우 나가면 방 삭제

### Estimated time
>Pick one

### `2.5h`

Start by locating the client roominfo component and the related database and roomlist flows. Verify each TODO case: remove the user and return to roomlist, transfer host authority when the host leaves, and delete the room when its last user leaves; the issue names no tests or specific files to run.

Written by the indexing model from the issue text.