ci: bump CD actions to Node 24 majors (checkout/docker)

GitHub is forcing Node 20 actions off the runners from 2026-06-02.
Bump checkout v4->v6 and the docker/* actions to their latest majors,
all of which run on Node 24. Inputs are unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: torrid-fish

.github/workflows/cd.yml

@@ -27,24 +27,24 @@ jobs:
       IMAGE_NAME: sessatakuma/api-tools
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
+        uses: docker/setup-qemu-action@v4
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@v4
 
       - name: Log in to GHCR
-        uses: docker/login-action@v3
+        uses: docker/login-action@v4
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Extract metadata
         id: meta
-        uses: docker/metadata-action@v5
+        uses: docker/metadata-action@v6
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
@@ -56,7 +56,7 @@ jobs:
             type=raw,value=stable,enable=${{ startsWith(github.ref, 'refs/tags/v') }}
 
       - name: Build and push
-        uses: docker/build-push-action@v6
+        uses: docker/build-push-action@v7
         with:
           context: .
           file: ./Dockerfile          # adjust if the api-tools Dockerfile path differs