Boulder (Plex): "flags every album, but everything has art." His albums show
art in the library (served from the embedded file art), but the DB thumb_url
cache column is empty — and the scan flagged on db_missing (empty thumb_url),
so every local album tripped it despite having perfectly good art in the files.
Now: a LOCAL album is flagged only when its files actually lack art
(disk_missing). An empty thumb_url is just a stale cache when the files have
art — not "missing cover art". db_missing still flags media-server-only albums
(no local files), where the DB thumb is the only art there is.
Tests: local+file-art+empty-thumb → NOT flagged (the bug); local+no-file-art →
still flagged; media-server-only+empty-thumb → still flagged.
7d481ae02f