Submits an image or PDF for forensic analysis. Supported formats: JPEG, PNG, HEIC, TIFF, WebP, GIF, BMP, PDF. Max file size: 100 MB. The file is forwarded to the Sentinel backend, a job is created, and the response is returned immediately with status 202 — poll GET /sentinel/jobs/{guid} or wire up a webhookUrl to be notified when analysis completes.