Move the resolution, bring-up, and orphan-cleanup logic out of
backend.py into three topic-named modules. DockerBottleBackend becomes
a thin façade that wires the per-instance pipelock proxy and the
provision orchestrator into the free functions.
backend.py drops from ~360 to ~70 lines and each topic now reads
end-to-end in one place. Mirrors the existing provision/ split.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
