[Client] 아이디어 리스트 페이지 기능 및 디자인 구현

### ISSUE
***
Group
- [ ] client
- [ ] server
- [ ] sr

Type
- [ ] bug
- [ ] feature
- [ ] add
- [ ] delete

description
> 아이디어 리스트페이지의 디자인과 기능을 구현합니다.

### TODO
***
1. [ ] job 1
2. [ ] job 2
3. [ ] job 3

### Estimated time
***
> 12h

The issue identifies a client-side idea list page but names no files, tests, or entry points. Start by locating the client application's idea list route and existing design patterns, then clarify jobs 1–3 and the intended behavior before making changes. Done means the page's specified design and functionality are implemented and verified.

Rédigé par le modèle d'indexation à partir du texte de l'issue.