[Task] dto와 class-validator를 적절히 활용하도록 수정

### ISSUE
- Detail: 유효성검사를 서비스쪽에서 하고있는데, class validator를 사용해보자

### TODO
1. [ ] dto 생성 후 타입교체
2. [ ] class validator를활용한 유효성검사

### 총 얼마나 걸리셨나요?
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No files, tests, or entry points are named. Start by locating the service-side validation and the relevant DTO or type definitions, then trace how requests are validated. Done means the types use DTOs and validation is handled with class-validator rather than in the service.

Written by the indexing model from the issue text.