* feat(lyrics): independent YouLyPlus toggle + all-sources-off state
Replace the binary lyricsMode ('standard' | 'lyricsplus') with an
independent youLyPlusEnabled flag so YouLyPlus and the standard sources
are no longer mutually exclusive — turning one off no longer forces the
other on. YouLyPlus (when on) is tried first with the enabled sources as
fallback; off uses only the enabled sources. When YouLyPlus is off and no
source is enabled, useLyrics fetches nothing (issue #810).
Fresh installs ship with every source off; the rehydrate migration only
restores the old on-by-default set for genuine upgrades, not new installs.
* feat(lyrics): YouLyPlus toggle UI + queue 'no sources' hint
Settings: single YouLyPlus toggle replacing the two mutually exclusive
mode switches; the source list is always visible with a context hint
(fallback vs primary). Queue lyric tab shows a hint when no source is
active. en + de strings; other locales fall back to en.
* docs(changelog): lyrics fully disablable (#855)
Frank Stellmacher
02b2df1589