Import an image from a URL

Import an image that is already hosted at a publicly reachable http(s) URL. The server downloads the image, verifies it really is one (PNG, JPEG, GIF, WebP, SVG or BMP; maximum 100 MB), stores a copy on the Gleap CDN, and returns the new permanent fileUrl. Useful for migrating help center article images in bulk when the files are already hosted elsewhere — import each image, then reference the returned URLs in the article content. URLs that resolve to private or internal network addresses are rejected.