backstage release v0.137.1

CI: prepare for the devctl-generated CircleCI config. The repo-specific jobs (the Node buildjob that feeds the image build, and the second control-plane-catalog chart push) move to .circleci/custom.yml; the .ats/main.yaml smoke-test config and a renovate-custom.json5 (preserving the repo’s Renovate reviewers, package groups, and schedule) are added so the upcoming generated config.yml/workflows.yml and regenerated renovate.json5 keep the existing behavior. See ./docs/releases/v0.137.1-changelog.md for more information.