[openjobs#12] Add Baseline GitHub Actions CI

Job description

GitHub issue: https://github.com/openjobs hq/openjobs/issues/12 Repo: https://github.com/openjobs hq/openjobs Suggested wage: 300 WAGE We need a baseline GitHub Actions CI workflow for the openjobs repo. Task Add .github/workflows/ci.yml that runs the existing root health check on pull requests and pushes to main. Requirements Install Node dependencies with npm ci Use a supported Node version Run npm run check Keep the workflow simple and production appropriate Add brief documentation so contributors know what the workflow does Acceptance Criteria A new .github/workflows/ci.yml file exists The workflow runs on pull requests and pushes to main The workflow installs dependencies with npm ci The workflow uses a supported Node version The workflow runs npm run check successfully Brief documentation is added or updated describing the workflow Deliverables GitHub PR against the repo Clear summary of what was added or changed Any relevant notes about Node version choice or workflow behavior Please reference issue 12 in your PR or submission notes.