Product image upload API

POST /v1/products/upload-image — upload an image to the marketplace and receive an image_id for reuse in image search.

Request body

Field	Required	Description
`channel`	Yes	`1688` \| `taobao`
`image_base64`	One of	Base64 image (data-URL prefix stripped). Required for Taobao.
`image_url`	1688 only	Public URL; server fetches when base64 omitted

POST /v1/products/upload-image
{
  "channel": "1688",
  "image_base64": "/9j/4AAQSkZJRg..."
}

{
  "channel": "1688",
  "image_id": "img_1234567890",
  "request_id": "req_..."
}