Migrate from Legacy to V1

Legacy is deprecated. New integrations must use V1. Keep the old endpoint only while you complete this migration.

Endpoint mapping

Legacy	V1
`POST /api/characters/preprocess`	`POST /v1/characters`
`/api/scenes/*`	`/v1/motions/*`
`POST /api/render`	`POST /v1/renders`
`GET /api/render/{job_id}`	`GET /v1/renders/{render_id}`
`DELETE /api/render/{job_id}`	`DELETE /v1/renders/{render_id}`
`GET /api/credits`	`GET /v1/credits`
`/api/extract/static-bin`	`POST /v1/avatars`
`/api/extract/dynamic-fbx`	`POST /v1/animations`

Legacy	V1
`scene_id`	`motion_id`
`job_id`	`id` with a `render_` prefix
`complete`	`ready`
`cdn_url`	`video_url`
`mask_cdn_url`	`alpha_url`
top-level error fields	nested `error` object with `code`, `message`, and `request_id`