add GitHub Actions workflow for Docker image build and GHCR push

[shubham3121]

This pull request introduces a new GitHub Actions workflow to automate building and publishing Docker images for the project. The workflow is triggered on pushes to the main branch and via manual dispatch, and it builds the frontend before creating and pushing the Docker image to GitHub Container Registry.

CI/CD automation:

• Added .github/workflows/docker-publish.yml to automate building and publishing Docker images on pushes to main and via workflow dispatch.

Frontend build integration:

• Installs frontend dependencies and builds the frontend using Bun before building the Docker image.

Docker image publishing:

• Uses Docker Buildx to build and push images, tagging them with both the short commit SHA and latest, and applies OCI labels for source and revision metadata.
• Implements build caching and passes a PYTHON_VERSION build argument for reproducible builds.