curl --request POST \
  --url https://app.autoposting.ai/api-proxy/clips/upload/presign \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "clipId": "<string>",
  "uploadId": "<string>",
  "partNumber": 123
}
'

{
  "success": true,
  "data": {
    "presignedUrl": "https://s3.amazonaws.com/bucket/...",
    "partNumber": 1
  }
}