랜딩페이지 목업 구현

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

### TODO
1. [ ] Job1 로그인, 회원가입, 체험하기 버튼 만들기
2. [ ] Job2 디자인(기능설명 페이지)이 들어갈 섹션 나눠두기

### Estimated time
> Pick one
### `0.5h`

### Labels
- Estimated time: `E: 1h`
- Group : `client`
- Sprint: `Sprint__NUMBER__`
- Urgency: `Middle`

Start in the client group and locate the landing-page entry point. Implement the login, sign-up, and trial buttons, then reserve sections for the feature explanations without adding the design. Done means the landing page contains these controls and separated sections; the issue names no specific file or test to run.

Written by the indexing model from the issue text.