Bake the internal Vault-PKI CA into a rebuild of
woodpeckerci/plugin-docker-buildx so k8s buildx jobs can push to
artifactapi's docker-internal registry over TLS.
- Dockerfile: copy unkin-ca.crt into /etc/docker/certs.d/<registry>/ca.crt
and the system trust store
- unkin-ca.crt: vault-ca-cert bundle (root + intermediate)
- .woodpecker/build.yaml: PR gate, buildah build-only
- .woodpecker/release.yaml: on v* tag, buildah build + credless push to
docker-internal with --tls-verify=false (bootstrap)
