Serve web-optimized image (max 2500px, original format)

The image at most 2500 px on its longest side, in its original format. An original that already fits is served as uploaded (has_canonical: false on the record); in the rare case the resizer could not shrink a very large original, that original is served too. With w, a lossy JPEG display rendition at most w px wide instead (never upscaled), or the file above where none is stored for that width: a rendition no lighter than the file is never kept, and an AI-generated image is never re-encoded.