feat(settings): appearance settings tab

New Appearance tab with color mode (moved out of Display), color-scheme swatches, a custom accent picker with a live WCAG contrast hint, transparency and reduce-motion toggles, density, a global text-size slider with advanced per-tier controls, and per-device dashboard widget toggles. Edits preview live and commit on a short debounce. i18n keys added across all locales, translated for German.

shared/src/i18n/ja/settings.ts

@@ -320,6 +320,48 @@ const settings: TranslationStrings = {
   'settings.aiParsing.multimodalHint': '画像認識対応モデル向け — 抽出したテキストの代わりに元のPDFを送信します。',
   'settings.aiParsing.toast.saved': 'AI設定を保存しました',
   'settings.aiParsing.toast.saveError': 'AI設定を保存できませんでした',
+  'settings.tabs.appearance': 'Appearance',
+  'settings.appearance.theme': 'Theme',
+  'settings.appearance.scheme': 'Color scheme',
+  'settings.appearance.scheme.default': 'Default',
+  'settings.appearance.scheme.highContrast': 'High contrast',
+  'settings.appearance.scheme.indigo': 'Indigo',
+  'settings.appearance.scheme.teal': 'Teal',
+  'settings.appearance.scheme.rose': 'Rose',
+  'settings.appearance.scheme.amber': 'Amber',
+  'settings.appearance.scheme.violet': 'Violet',
+  'settings.appearance.scheme.custom': 'Custom',
+  'settings.appearance.customAccent': 'Custom accent',
+  'settings.appearance.contrastOk': 'Good contrast',
+  'settings.appearance.contrastLow': 'Low contrast',
+  'settings.appearance.readability': 'Readability',
+  'settings.appearance.transparency': 'Transparency',
+  'settings.appearance.transparencyHint': 'Glassy translucent surfaces. Turn off for solid, higher-contrast backgrounds.',
+  'settings.appearance.reduceMotion': 'Reduce motion',
+  'settings.appearance.reduceMotionHint': 'Minimize animations and transitions.',
+  'settings.appearance.density': 'Density',
+  'settings.appearance.comfortable': 'Comfortable',
+  'settings.appearance.compact': 'Compact',
+  'settings.appearance.textSize': 'Text size',
+  'settings.appearance.advancedTextSizes': 'Advanced text sizes',
+  'settings.appearance.hideAdvanced': 'Hide advanced',
+  'settings.appearance.tier.title': 'Titles',
+  'settings.appearance.tier.subtitle': 'Subtitles',
+  'settings.appearance.tier.body': 'Body',
+  'settings.appearance.tier.caption': 'Captions',
+  'settings.appearance.dashboardWidgets': 'Dashboard widgets',
+  'settings.appearance.dashboardWidgetsHint': 'Show or hide dashboard widgets independently on desktop and mobile.',
+  'settings.appearance.desktop': 'Desktop',
+  'settings.appearance.mobile': 'Mobile',
+  'settings.appearance.widget.sidebar': 'Right sidebar',
+  'settings.appearance.widget.currency': 'Currency',
+  'settings.appearance.widget.timezones': 'Timezones',
+  'settings.appearance.widget.upcomingReservations': 'Upcoming reservations',
+  'settings.appearance.widget.atlas': 'Atlas / countries',
+  'settings.appearance.widget.tripsTotal': 'Trips total',
+  'settings.appearance.widget.daysTraveled': 'Days traveled',
+  'settings.appearance.widget.distanceFlown': 'Distance flown',
+  'settings.appearance.reset': 'Reset to defaults',
 };
 
 export default settings;