Fetches album cover bytes via the authenticated dio and writes to
<applicationCacheDirectory>/album_covers/<albumId>.jpg. Returns the
local path so MediaItem.artUri can point at a file:// URI — Android's
MediaSession framework fetches artUri itself without our Bearer
header, so a pre-fetched local file is the workaround.
Concurrent callers for the same albumId dedupe to one fetch via an
in-flight Future map. Any failure (network / 4xx / 5xx / disk full /
empty id) returns null without throwing — playback continues with
the system's generic music icon, same UX as today.
No eviction — covers are tiny, OS clears cache when space is tight.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
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