ci: bump checkout@v5 and setup-buildx-action@v4 (Node 24, drop deprecation)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: programmerShinobi

.github/workflows/ci.yml

@@ -15,10 +15,10 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
 
       - name: Create .env for CI
         run: |