Synced lyrics (OpenSubsonic songLyrics) #11

Navidrome serves synced lyrics via the OpenSubsonic songLyrics extension (getLyricsBySongId), and it's become a standard client feature in this space.

Sketch: a lyrics pane in the Now Playing panel (toggle below the hero), highlighting the current line from the timestamped lyrics; plain unsynced fallback when timestamps are absent. Optional later: LRCLIB fallback for servers without lyrics — network egress beyond the user's server should be opt-in.