feat(settings): theme scheduler, UI scale, CustomSelect scroll fix

- Time-based theme scheduler: auto-switches between day/night theme
  based on configurable times; setInterval re-checks every minute
- UI scale slider (80–150%) via CSS zoom on document root; preset
  buttons aligned to actual slider positions
- CustomSelect: scroll listener keeps dropdown anchored on scroll
- All features i18n in 7 languages

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

src/locales/fr.ts

@@ -572,6 +572,15 @@ export const frTranslation = {
     seekbarParticletrail: 'Traînée de particules',
     seekbarLiquidfill: 'Tube liquide',
     seekbarRetrotape: 'Bande rétro',
+    themeSchedulerTitle: 'Planificateur de thème',
+    themeSchedulerEnable: 'Activer le planificateur de thème',
+    themeSchedulerEnableSub: 'Bascule automatiquement entre deux thèmes selon l\'heure',
+    themeSchedulerDayTheme: 'Thème de jour',
+    themeSchedulerDayStart: 'Début du jour',
+    themeSchedulerNightTheme: 'Thème de nuit',
+    themeSchedulerNightStart: 'Début de la nuit',
+    uiScaleTitle: "Mise à l'échelle de l'interface",
+    uiScaleLabel: 'Zoom',
   },
   changelog: {
     modalTitle: 'Quoi de neuf',