This commit enhances our GitHub Actions workflow to support multi-architecture 
Docker builds with proper digest handling. Key changes include:

- Build and push Docker images for amd64, arm64, arm/v6, and arm/v7 architectures
- Implement digest collection and artifact uploading for each architecture
- Create a manifest list combining all architecture-specific images
- Add conditional execution to skip pushes on pull requests
- Improve error handling and add Docker logout steps for security

These updates enable us to efficiently build and distribute our Docker images 
across multiple architectures, improving compatibility and streamlining our 
deployment process. Users can now pull the appropriate image for their system 
architecture automatically.