fix: update GitHub Actions to use actions/cache@v4 and actions/checkout@v4

Updates deprecated actions/cache@v2 and actions/checkout@v2 to v4 to avoid workflow interruptions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dragonee

.github/workflows/deploy.yml

@@ -13,8 +13,8 @@ jobs:
   deploy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/cache@v2
+      - uses: actions/checkout@v4
+      - uses: actions/cache@v4
         with:
           path: /tmp/composer-cache
           key: ${{ runner.os }}-${{ hashFiles('**/composer.lock') }}