Update Docker config: opt into Node.js 24 actions, rename to check-printing

- Add FORCE_JAVASCRIPT_ACTIONS_TO_NODE24=true to docker-build workflow
- Switch login step to vars.DOCKERHUB_USERNAME (non-secret)
- Rename docker-compose service, container, volume, and DB file to check-printing

.github/workflows/docker-build.yml

@@ -8,6 +8,7 @@ on:
 
 env:
   IMAGE_NAME: ${{ secrets.DOCKERHUB_USERNAME }}/check-printing
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
 
 jobs:
   build-push:
@@ -26,7 +27,7 @@ jobs:
       - name: Log in to Docker Hub
         uses: docker/login-action@v3
         with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Extract image metadata