Prefix all image names with docker.io/ to avoid registry ambiguity
on hosts where containerd/Podman default to docker.io but the pull
fails without an explicit registry prefix.
Also marks T07 (smoke-test Temporal cluster and UI) as done in the
workplan now that the stack boots cleanly.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>