Lightweight status check for a presigned upload slot. Returns the SAME state as `GET /media/uploads/{id}` but with NO body — the status is carried in the `X-Reveldigital-Upload-Status` header (`pending`, `uploaded`, or `completed`) and, once finalized, the media id in `X-Reveldigital-Media-Id`. This lets a client cheaply poll for completion without transferring or parsing a JSON body.