회원탈퇴 라우팅 및 기능 구현

### ISSUE

- Group: `server`
- Type: `feature`
- Detail: 회원탈퇴 라우팅 및 기능 구현

### TODO

- [x] 회원일 경우, db에서 삭제 후
- [x] 회원이 아닐 경우, {success:true} 발송(200)
- [x] 일치하는 회원이 없을 경우, {success:false} 발송(404)

### Estimated time
>Pick one

### `3h`

### Labels

- Estimated time: `E: 3h`
- Group: `server`
- Sprint: `Sprint__NUMBER__2`
- Urgency: `High`

No file or test is named; start by locating the server's member routes and database access entry points. Check the existing member-deletion flow and verify the three listed outcomes, including their response bodies and HTTP statuses, before considering the work done.

Written by the indexing model from the issue text.