v1 dropped node:20-bookworm for a Node-free Debian base, on the wrong
assumption that nothing in CI needs Node since the frontend is Go now.
Forgejo's runner executes actions/checkout@v4 as `node dist/index.js`
inside the job container regardless of what the workflow itself runs,
so every job's checkout step failed. Caught from the live run within
a minute; runner was reverted to node:20-bookworm immediately.
v2 keeps the node:20-bookworm base and only adds docker-ce-cli +
docker-buildx-plugin on top, preserving the actual fix (BuildKit
instead of the classic builder, no per-job docker.io install) without
removing a hard dependency.
Image is live at git.thermograph.org/emi/thermograph/ci-runner:v1.
register-lan-runner.sh's LABELS default now points at it, and the
live runner's registration was cut over directly (labels edited in
~/forgejo-runner/.runner, no re-registration needed).
