feat: make docker-compose use PORT env variable and .env file

[keebOo]

Changes

• Added env_file: - .env to load environment variables from .env file
• Changed port mapping from hardcoded 3000:3000 to ${PORT:-3000}:${PORT:-3000}
• This allows users to customize the port via the PORT environment variable
• Maintains backward compatibility with default port 3000

Benefits

• More flexible port configuration
• Consistent with the existing PORT environment variable support
• Follows Docker Compose best practices for environment variable usage

[trgwii]

This seems like a strange workflow. When I want to use a docker-compose file, I put it in a folder, edit it, and run docker compose up. Is that not a common workflow? Can you link to some Docker documentation on the "best practices" you're referring to?