Use object-fill for compact preview thumbnails so rank-list covers and
file previews fill their fixed boxes without cropping or black bars. This
keeps the list layout stable while matching the desired compressed-ratio
thumbnail treatment.
Successful downloads no longer pop a 'downloadOk' toast across all
the download sites (PopularRankList, RecommendedCard, FileDocBubble,
ImageLightbox). The browser's native download UI already confirms
the action, and the toast was redundant noise. Failure toasts and
the spinner state remain so users still see errors.
