Register jobs for later use

Registers one or more uploaded or externally hosted file URLs as Lingopal media/document records. This endpoint records source metadata only; processing inputs such as target languages and translation context are supplied later through the appropriate `/v2/jobs/{job_id}` workflow endpoint. Per-item failures are returned in the `results` array with `status="error"`.

curl -X POST "https://example.com/v2/jobs/register" \  -H "Content-Type: application/json" \  -d '{    "items": [      {        "source_url": "https://example-bucket.s3.amazonaws.com/presigned_upload/user_123/product-demo.mp4",        "name": "Product Demo",        "media_type": "video"      }    ]  }'

{  "message": "Job registration completed",  "registered_count": 1,  "error_count": 0,  "results": [    {      "name": "Product Demo",      "source_url": "https://cdn.example.com/uploads/product-demo.mp4",      "status": "registered",      "job_id": "job_123",      "media_type": "video"    }  ]}