[Feat] 아래에서 올라오던 알림 두 곳을 위에서 내려오는 토스트로 통일합니다 - #280

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