Add automated Docker image build and publish workflow

[znhocn]

Summary

This Pull Request introduces a GitHub Actions workflow to automatically build and publish Docker images to GitHub Container Registry (GHCR).

The workflow establishes a consistent image build and tagging strategy, supports multi-architecture builds, and is compatible with both personal and organization repositories.

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Proposed Changes

1. Automated Docker image builds

• Build Docker images on pushes to the main branch
• Build and publish images on versioned Git tags (vX.Y.Z)
• Pull request builds run for validation only and do not publish images

2. Consistent image tagging strategy

• Branch builds publish branch and commit SHA tags
• Tag builds publish versioned tags and latest
• Non-release builds do not overwrite the latest tag

3. Multi-architecture support

• Build images for linux/amd64 and linux/arm64

4. Build cache optimization

• Use GitHub Actions cache to speed up subsequent builds

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Image Tag Behavior

Trigger type	Published tags
Pull Request	build only (no publish)
Push to main	main, sha-<commit>
Git tag vX.Y.Z	vX.Y.Z, latest, sha-<commit>

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Motivation

• Establish an automated and repeatable Docker image build process
• Provide predictable and controlled image tagging for releases
• Align container publishing behavior with common best practices
• Ensure compatibility across different repository ownership models

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Checklist

• Workflow runs successfully on pull requests
• Images are published on main branch pushes
• Release tags publish versioned and latest images
• Compatible with personal and organization repositories

[willbert03]

This is a really good idea. It will make it easier to spin up a local version of the web app and run it on different devices. I hope this is implemented soon.