[프론트엔드] <BoardContent> 페이지 구현

## ISSUE
- Group: `client`
- Type: `feature`
- Detail: 페이지 구현

## TODO
- [ ] 날짜 창
- [ ] 사진 창
- [ ] 어종이름 select
- [ ] 크기 창(소수점 1자리까지만 가능)
- [ ] 취소버튼
- [ ] 저장버튼
- [ ] 저장되었습니다 알림

## Estimated time
`1.5h`

## Labels
Estimated time: E: `1.5h`
Group : `client`
Sprint: `Sprint 1`
Urgency: `bare`

Start in the client frontend by locating the page entry point. Review the existing page patterns and implement the listed date, photo, fish-name select, size, cancel, save, and saved-notification elements; done means all TODO items work, including one decimal place for size.

Written by the indexing model from the issue text.