cmotion api

POST /v1/render          { source, params? }  →  202 { job_id }
POST /v1/frame           { source, params? }  →  202 { job_id }
GET  /v1/jobs/<id>                              →  status + url when ready
GET  /v1/outputs/<file>                          →  streams the render
GET  /test                                       →  synchronous smoke test
GET  /healthz                                    →  liveness