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/en.ts

@@ -853,6 +853,12 @@ export const enTranslation = {
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (tagged files)',
     replayGainFallback: 'Fallback (untagged / radio)',
+    normalization: 'Normalization',
+    loudnessTargetLufs: 'Target LUFS',
+    loudnessPreAnalysisAttenuation: 'Trim before measurement (dB)',
+    loudnessPreAnalysisAttenuationDesc:
+      'Extra quieting until loudness for this track is saved. Streaming then uses rough guesses, not a full measurement. 0 dB = off; lower = quieter.',
+    loudnessPreAnalysisAttenuationReset: 'Reset to default',
     crossfade: 'Crossfade',
     crossfadeDesc: 'Fade between tracks',
     crossfadeSecs: '{{n}} s',