Ingest a compose YAML document

Upload a compose YAML body so the daemon owns the parsed project state. Subsequent up/down/restart calls operate against the ingested document. Idempotent on byte-identical re-uploads (200); differing content under the same project name yields 409.

Documents containing include: directives are rejected — uploaded compose is evaluated without filesystem context. CHAOS-1426 (Decision #12 follow-up).