Update Docker build process for new version

[djthorpe]

This pull request updates the Docker build workflow to improve consistency, reliability, and compatibility with newer GitHub Actions and Docker best practices. The main changes include updating action versions, improving environment variable usage, and adjusting Docker tagging and manifest creation logic.

Workflow and Docker build improvements:

• Updated the workflow to trigger on published releases instead of created for more accurate Docker image publishing.
• Updated the runner images to use Ubuntu 24.04 for both amd64 and arm64 architectures for better compatibility and consistency.
• Upgraded actions/checkout to v6 and docker/login-action to v4, and improved git and submodule handling for more reliable builds.
• Changed Docker image tagging and manifest logic to use consistent environment variables and improved tag formatting, matching the Makefile and reducing duplication. [1] [2]
• Updated the Makefile’s DOCKER_TAG format to align with the workflow, ensuring tags are predictable and consistent across build and deployment steps.

[Copilot]

Pull request overview

This pull request updates the Docker image build/publish pipeline to align with newer GitHub Actions runners/actions and to standardize Docker tagging + manifest creation across architectures.

Changes:

• Switch release trigger from created to published and centralize Docker-related env vars in the workflow.
• Update build runners to Ubuntu 24.04 (including ARM runner) and bump actions/checkout + docker/login-action major versions.
• Normalize Docker image tags to ${DOCKER_REPO}:${VERSION}-${OS}-${ARCH} and update manifest creation to match.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Makefile	Updates Docker tag format used by make docker / make docker-push to match multi-arch manifest expectations.
.github/workflows/docker.yaml	Updates release trigger, runner images, action versions, and manifest/tag logic for consistent multi-arch publishing.

Comments suppressed due to low confidence (1)

.github/workflows/docker.yaml:11

• DOCKER_SOURCE is now set to github.com/${{ github.repository }} (no scheme). The Dockerfile uses this value for org.opencontainers.image.source, which is expected to be a URL; dropping https:// makes the label less useful and differs from the Dockerfile default.

env:
    DOCKER_REPO: ghcr.io/${{ github.repository_owner }}/pgmanager
    DOCKER_SOURCE: github.com/${{ github.repository }}

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[github-actions]

Coverage for this change: 62.4%