The external network on the target server is named "proxy", not
traefik-network as originally assumed - deploy was failing with
"network traefik-network not found". Updated the compose file and
both the infra README and vault deployment doc to match.
migrate/api/worker/frontend now reference
git.devils.zone/devil/youtube-studio-flow-{backend,frontend}:\${IMAGE_TAG}
instead of building on the deploy host. Adds scripts/build-and-push.sh
to build+tag (git short SHA + latest) and push both images from a dev
machine, and updates infrastructure/README.md with the pull-based
deploy sequence.