Album art embedding now tries Cover Art Archive first (using the
MusicBrainz release ID from source ID embedding) before falling back
to Spotify/iTunes/Deezer URLs. CAA provides original-quality artwork,
often 1200x1200 or higher vs Spotify's 640x640 max.
Reordered _embed_source_ids to run before _embed_album_art_metadata
so the MusicBrainz release ID is available for the CAA lookup. Also
fixed hardcoded 640x640 FLAC picture dimensions — now detects actual
size from image bytes. Falls back to existing behavior if CAA fails
or no release ID exists.
a803e8399c
