feat(lyrics): configurable sources with drag-to-reorder + feat(audio): ReplayGain pre-gain & fallback

Lyrics Sources:
- Replace lyricsServerFirst + enableNeteaselyrics toggles with a new
  Settings section — three sources (Server, LRCLIB, Netease) each
  individually toggled and drag-reorderable via psy-drop DnD
- useLyrics.ts iterates sources in user-defined order, skipping disabled
  ones; embedded SYLT from local files still wins unconditionally
- onRehydrateStorage migration from legacy fields on first load

ReplayGain Pre-Gain:
- New authStore fields: replayGainPreGainDb (0…+6 dB) and
  replayGainFallbackDb (-6…0 dB, untagged / radio)
- audio.rs compute_gain applies pre_gain_db and fallback_db
- Settings sliders under ReplayGain mode selector
- Radio HTML5 volume scaled by fallbackDb factor on playRadio

i18n(ru): incorporate PR #148 translation improvements (kilyabin)
All 7 locales updated for new keys.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/locales/nb.ts

@@ -488,6 +488,11 @@ export const nbTranslation = {
     lyricsServerFirstDesc: 'Sjekk tjenerlevererte sangtekster (innebygde tagger, sidecar-filer) før LRCLIB. Deaktiver for å bruke LRCLIB først.',
     enableNeteaselyrics: 'Netease Cloud Music sangtekster',
     enableNeteaselyricsDesc: 'Bruk Netease Cloud Music som siste utvei når server og LRCLIB ikke finner noe. Best dekning for asiatisk og internasjonal musikk.',
+    lyricsSourcesTitle: 'Sangtekstkilder',
+    lyricsSourcesDesc: 'Velg hvilke kilder som skal brukes og i hvilken rekkefølge. Dra for å sortere. Deaktiverte kilder hoppes over.',
+    lyricsSourceServer: 'Tjener',
+    lyricsSourceLrclib: 'LRCLIB',
+    lyricsSourceNetease: 'Netease Cloud Music',
     downloadsTitle: 'ZIP Eksport & Arkivering',
 	downloadsFolderDesc: 'Målmappe for album du laster ned som en ZIP-fil til datamaskinen din.',												  
     downloadsDefault: 'Standard nedlastingsmappe',
@@ -571,6 +576,8 @@ export const nbTranslation = {
     replayGainMode: 'Modus',
     replayGainTrack: 'Spor',
     replayGainAlbum: 'Album',
+    replayGainPreGain: 'Pre-Gain (taggede filer)',
+    replayGainFallback: 'Reserveverdi (uten tagger / radio)',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Tone mellom spor',
     crossfadeSecs: '{{n}}s',