feat: AtchaV2 Phase 9 — LA 빌드 인프라 (위젯 익스텐션 + CoreLiveActivity + entitlements) - #347

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/