ci: add Docker build and ghcr push to CI pipeline

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Summary

• Adds a docker job to CI that runs after e2e tests pass
• On PRs: builds the Docker image only (validates Dockerfile)
• On main: checks if version from package.json already exists in ghcr, fails if so, otherwise pushes ghcr.io/null-ptr-exception/rulemgmt:<version> and latest
• Uses BuildKit with GitHub Actions cache

Test plan

• PR CI builds Docker image without pushing
• Merge to main pushes image to ghcr with correct version tag
• Duplicate version push fails with clear error message

Summary by CodeRabbit

• Chores
  • Enhanced CI pipeline with automated Docker image building and publishing to container registry, including version management to prevent duplicate releases.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Free

Run ID: 0ef056f0-2542-4801-b480-652817d8eaac

📥 Commits

Reviewing files that changed from the base of the PR and between 921553c and 401542d.

📒 Files selected for processing (1)

• .github/workflows/ci.yml

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📝 Walkthrough

Walkthrough

A new docker job is added to the CI workflow that automatically builds and pushes Docker images to GitHub Container Registry. The job reads the application version from package.json, validates that the image tag does not already exist on the main branch, and conditionally builds and pushes the image with both version and latest tags using Docker Buildx.

Changes

Docker Image Build and Push

Layer / File(s)	Summary
Docker build and push job with GHCR validation .github/workflows/ci.yml	New docker job runs after e2e completion, reads version from package.json, checks GHCR for existing image tags on main, fails if tag already exists, and conditionally builds and pushes the Docker image to ghcr.io with version and latest tags using Docker Buildx with GitHub Actions caching.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A Docker job joins the CI chain,
Reading versions, checking the main,
If tags don't clash, the image will flow,
To the registry, latest in tow!

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Note

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