Add a PR-targeted Docker build check so each pull request validates container buildability before merge.
- Add .github/workflows/docker-pr-build.yml, or equivalent logic folded into an existing workflow
- Trigger on pull_request for backend-relevant file changes
- Run docker build for the backend image
- Fail PR checks if dependency resolution or build fails
- Keep runtime minimal by using caching where possible
Add a PR-targeted Docker build check so each pull request validates container buildability before merge.