Backend now stores AVIF, WebP, JPEG, and optional JXL variants for both full-size and thumbnail images. Database schema extended with 7 new columns. Image validation supports AVIF and JXL magic bytes. Comprehensive test coverage for all format URL fields and magic byte detection. Legacy single-URL images remain backward-compatible.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
popertotsandSisyphus