The offline short-circuit in fetch_cached_http gated ALL its consumers,
including ArtworkRef::PlexThumb - the LAN artwork of local-library Plex
rows. Misses were guaranteed across surfaces because the server-transcode
size is part of the URL cache key (queue 96 / song card 160 / grid 264),
so covers cached by the grid still missed everywhere else while offline.
fetch_cached_http now takes a gate_offline flag: Remote (Qobuz CDN) keeps
the offline gate, PlexThumb bypasses it (LAN is not the internet; a dead
LAN attempt is bounded by the 10s client timeout).
cc
vicrodh
210b8020d3