Adds workplan for containerising KeyCape and publishing to the self-hosted
Gitea registry on CoulombCore (92.205.130.254:32166) instead of GHCR. Covers
Makefile targets, Gitea Actions workflow, k3s insecure registry config, machine
account/token management, and a smoke test round-trip.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>