fix(seekbar): split waveform style into truewave (analyzed) + pseudowave (deterministic)

The waveform-loudness-cache merge replaced the existing deterministic
per-track-ID waveform with a bins-based one driven by the analysis
cache. The bins-based variant is the better default but the old
deterministic look is still valuable when no analysis is available
(brand-new track, cache-miss, etc.) and several users prefer it.

Split into two explicit options in the seekbar style picker:

- 'truewave' (default, replaces old 'waveform') — bins from the analysis
  cache, with morph-on-arrival animation and flat-line fallback while
  empty.
- 'pseudowave' — pseudo-random heights derived deterministically from
  the track ID. No analysis dependency, no morph, instant render.

Existing persisted seekbarStyle: 'waveform' is migrated to 'truewave'
in onRehydrateStorage so users keep the visual they have today. The
useEffect that builds heightsRef now lists seekbarStyle in its deps so
switching between the two is live.

i18n labels added in all 8 locales.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/pages/Settings.tsx

@@ -3676,7 +3676,7 @@ export default function Settings() {
                 {t('settings.seekbarStyleDesc')}
               </div>
               <div style={{ display: 'flex', flexWrap: 'wrap', gap: 10 }}>
-                {(['waveform', 'linedot', 'bar', 'thick', 'segmented', 'neon', 'pulsewave', 'particletrail', 'liquidfill', 'retrotape'] as SeekbarStyle[]).map(style => (
+                {(['truewave', 'pseudowave', 'linedot', 'bar', 'thick', 'segmented', 'neon', 'pulsewave', 'particletrail', 'liquidfill', 'retrotape'] as SeekbarStyle[]).map(style => (
                   <SeekbarPreview
                     key={style}
                     style={style}