ui(settings): restructure Normalization section for clarity and breathing room

The mode picker (Off / ReplayGain / LUFS) used to live in the right-hand
action slot of a settings-toggle-row and the per-mode controls were
stacked into the same parent with footer-style help text. Hard to scan,
visually cramped, and odd compared to the rest of the Settings page.

Refactor:

- Mode picker becomes a full-width segmented row with even-flex buttons,
  using the new .settings-segmented utility.
- Each mode renders its own .settings-norm-block sub-section with a
  subtle accent tint and border so the active configuration reads as
  one coherent group.
- Inside the block, every setting is its own .settings-norm-field
  (control row + per-control help text immediately below). 1.1 rem gap
  between fields, 0.45 rem between row and help — clearly groups
  related text without crowding.
- Sliders no longer max-cap at 200 px and instead flex to fill the row.
- Inactive ghost buttons (Off, ReplayGain, RG mode, LUFS targets) get a
  visible border and a faint surface tint so they read as selectable
  slots in dark themes too.
- LUFS mode gets a dedicated note-box explaining that brief volume drift
  on the very first play of a new track is the analysis pass at work,
  not a bug — subsequent plays use the cached measurement, and queued
  tracks are usually pre-analysed during the previous song.
- "Trim before measurement (dB)" renamed to "Pre-analysis attenuation"
  (and equivalents in 8 locales).
- New i18n keys: normalizationDesc, normalizationOff/ReplayGain/Lufs,
  loudnessTargetLufsDesc, loudnessFirstPlayNote, replayGainPreGainDesc,
  replayGainFallbackDesc.

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

src/locales/nl.ts

@@ -833,13 +833,22 @@ export const nlTranslation = {
     replayGainTrack: 'Nummer',
     replayGainAlbum: 'Album',
     replayGainPreGain: 'Pre-Gain (getagde bestanden)',
+    replayGainPreGainDesc: 'Universele boost bovenop elke ReplayGain-berekening. Handig als je bibliotheek over het geheel te zacht aanvoelt.',
     replayGainFallback: 'Terugval (zonder tags / radio)',
+    replayGainFallbackDesc: 'Toegepast op nummers (en radiostreams) zonder ReplayGain-tags, zodat ongetagde inhoud er niet harder uitspringt dan de rest.',
     normalization: 'Normalisatie',
+    normalizationDesc: 'Egaliseer de waargenomen luidheid tussen nummers, albums en radio.',
+    normalizationOff: 'Uit',
+    normalizationReplayGain: 'ReplayGain',
+    normalizationLufs: 'LUFS',
     loudnessTargetLufs: 'Doel-LUFS',
-    loudnessPreAnalysisAttenuation: 'Demping vóór meting (dB)',
+    loudnessTargetLufsDesc: 'Referentie-luidheid waarop alle nummers worden afgestemd. Lagere waarde = luidere uitvoer. Streamingdiensten zitten meestal rond -14 LUFS.',
+    loudnessPreAnalysisAttenuation: 'Demping vóór meting',
     loudnessPreAnalysisAttenuationDesc:
       'Extra zachter tot de loudness van het nummer is opgeslagen. Streamen gebruikt daarna grove schattingen, geen volledige meting. 0 dB = uit; negatiever = zachter.',
     loudnessPreAnalysisAttenuationReset: 'Standaard',
+    loudnessFirstPlayNote:
+      'Bij de eerste keer afspelen van een nieuw nummer kan het volume even fluctueren terwijl er gemeten wordt. De volgende keer gebruikt de speler de opgeslagen meting en blijft alles rotsvast. Komende nummers in de wachtrij worden meestal al tijdens het vorige nummer geanalyseerd, dus dit komt in de praktijk zelden voor.',
     crossfade: 'Overgang',
     crossfadeDesc: 'Fade tussen nummers',
     crossfadeSecs: '{{n}} s',