curl --request POST \
  --url https://app.autoposting.ai/api-proxy/kbs/{kbId}/docs/upload \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form file='@example-file'

{
  "success": true,
  "data": {
    "id": "doc_01HXYZ",
    "name": "doc.pdf",
    "status": "processing",
    "createdAt": "2024-01-01T00:00:00Z"
  }
}