Append product photos (upload or import by URL)

Appends images to the gallery file field (gallery+); stored images stay in place.

• Content-Type: application/json expects { urls }: the server downloads every http(s) URL (15 s timeout each). Any failed download answers 400 with the message of the first failure.
• Any other content type is read as multipart/form-data; every files part is one image.

A component holds at most 8 images in total; each image must be at most 5 MB and of type image/png, image/jpeg, image/webp, image/avif, image/svg+xml. On success the cached component reads and the public pages /components and /components/<slug> are revalidated.