feat(playback): loudness bind rules, analysis seeding, and normalization UI

Resolve integrated loudness from SQLite only at decode bind; keep pre-trim
until a row exists, then allow provisional gain from live updates. Pass
DB-stable hints from the web app into play and gapless preload.

Default pre-measurement attenuation -4.5 dB with an icon reset in Settings;
drop redundant normalization copy and shorten pre-trim descriptions.

analysis_cache seed_from_bytes returns an outcome and skips redundant
waveform work on cache hits; wire callers and related frontend/backend glue.

src/locales/es.ts

@@ -840,6 +840,12 @@ export const esTranslation = {
     replayGainAlbum: 'Álbum',
     replayGainPreGain: 'Pre-Ganancia (archivos etiquetados)',
     replayGainFallback: 'Respaldo (sin etiquetar / radio)',
+    normalization: 'Normalización',
+    loudnessTargetLufs: 'LUFS objetivo',
+    loudnessPreAnalysisAttenuation: 'Atenuación antes de medir (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Atenúa hasta que la loudness del tema esté guardada. En streaming luego solo hay estimaciones aproximadas. 0 dB = ninguna; más negativo = más bajo.',
+    loudnessPreAnalysisAttenuationReset: 'Predeterminado',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Transición entre pistas',
     crossfadeSecs: '{{n}} s',