psviderski/unregistry: Push docker images directly to remote servers without an external registry

Unregistry is a lightweight container registry that enables direct Docker image transfers to remote servers over SSH without requiring external registries. The tool includes a 'docker pussh' command that transfers only missing image layers, making deployments faster and more efficient. It eliminates the need for Docker Hub subscriptions, self-hosted registries, or inefficient save/load operations by establishing SSH tunnels and using temporary registry containers for direct image transfers.