Generalize resolve_album_cover_fallback beyond a single track + cover.jpg:
scan several of the album's tracks (CMAF keeps each track in its own folder,
only some of which may carry a cover), check both the track folder and its
parent (multi-disc layouts keep art one level up), and accept the common
local cover filenames (cover/folder/front, jpg/png). Resolves more on-disk
covers without touching the paged query. Albums whose offline bundle never
saved a cover (segments only) still need an offline-cache cover re-fetch.
cc
vicrodh
b412293f3c