Add CI rollout baseline

[ohmyfelix]

What changed

• Split Docker workflow into Test, Build, and Docs jobs while preserving the Docker CLI image matrix.
• Added Makefile build, test, and run aliases with Docker CLI, Compose, and make smoke checks.
• Normalized README badges to the Dockette style and removed the legacy Gitter badge.

Why

• Establishes the Dockette CI rollout baseline for dockette/docker, including Docker Hub description publishing and canonical project metadata.