[design] 공통 디자인 컨벤션 및 타이포그래피 기반 정립 - #536

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4, actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

React Hook useEffect has a missing dependency: 'socket'. Either include it or remove the dependency array