serveEntity reads persisted item_artwork by id, bypassing the library and private-
playlist filters that the legacy entity-load applied. On the authenticated Subsonic
path a user could fetch artwork for an inaccessible album or someone else's private
playlist by guessing an id. getCoverArt now resolves the underlying entity through
the request-scoped (filtered) repositories and serves the placeholder when it is not
visible, so existence isn't leaked and the always-an-image invariant holds. The
public share (JWT-authorized) and Jellyfin (admin) paths are intentionally untouched.
DiscCoverArtID returns a dc- id for any track with DiscNumber>0, so serveDisc ran
the full DiscArtPriority chain even for single-disc albums, where a stray disc*/
embedded image could shadow higher-priority album art. Gate disc resolution on the
album having more than one disc, matching the legacy reader; single-disc tracks
serve album art directly.
serveMediaFile delegated an absent/ineligible track straight to AlbumCoverArtID,
skipping the disc-specific lookup that MediaFile.CoverArtID (and the deleted legacy
reader) use. On multi-disc albums with per-disc images that served the album cover
instead of the configured disc artwork. Delegate through DiscCoverArtID.
The provisional read-through and dangling re-enqueue used Enqueue, whose upsert
resets retry_at, so any browse of an unresolved entity that was backing off after
an external failure made it immediately eligible again — defeating the exponential
backoff during a provider outage. Add EnqueueBump, which raises priority but leaves
an existing row's retry_at intact, and route the serving path through it. Scan and
manual re-resolve keep Enqueue's reset (a detected change wants immediate retry).
