fix: address review feedback on the distance unit setting

- server: allow distance_unit as an admin default (+ value validation) so the
  Admin "Default User Settings" toggle persists instead of returning 400
- i18n: add settings.distance to all 20 locales and translate the labels
  through t() instead of hardcoding "Distance"
- route legs: include the unit in the OSRM cache key and recompute on a unit
  switch, so map and sidebar distances refresh and never mix units
- keep wind speed tied to the temperature unit — a distance setting must not
  silently flip existing Fahrenheit users from mph to km/h
- restore the sub-1km metres reading for metric, convert GPX elevation to feet
  for imperial, and format distances with a '.' decimal in every locale
- add units.test.ts

shared/src/i18n/ar/settings.ts

@@ -51,6 +51,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'تلقائي',
   'settings.language': 'اللغة',
   'settings.temperature': 'وحدة الحرارة',
+  'settings.distance': 'وحدة المسافة',
   'settings.timeFormat': 'تنسيق الوقت',
   'settings.bookingLabels': 'تسميات مسارات الحجوزات',
   'settings.bookingLabelsHint': 'عرض أسماء المحطات/المطارات على الخريطة. عند الإيقاف، يتم عرض الرمز فقط.',

shared/src/i18n/br/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automático',
   'settings.language': 'Idioma',
   'settings.temperature': 'Unidade de temperatura',
+  'settings.distance': 'Unidade de distância',
   'settings.timeFormat': 'Formato de hora',
   'settings.blurBookingCodes': 'Ocultar códigos de reserva',
   'settings.optimizeFromAccommodation': 'Otimizar rota a partir da hospedagem',

shared/src/i18n/cs/settings.ts

@@ -53,6 +53,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatické',
   'settings.language': 'Jazyk',
   'settings.temperature': 'Jednotky teploty',
+  'settings.distance': 'Jednotky vzdálenosti',
   'settings.timeFormat': 'Formát času',
   'settings.blurBookingCodes': 'Skrýt rezervační kódy',
   'settings.optimizeFromAccommodation': 'Optimalizovat trasu od ubytování',

shared/src/i18n/de/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatisch',
   'settings.language': 'Sprache',
   'settings.temperature': 'Temperatureinheit',
+  'settings.distance': 'Entfernungseinheit',
   'settings.timeFormat': 'Zeitformat',
   'settings.bookingLabels': 'Orts-Labels auf Buchungsrouten',
   'settings.bookingLabelsHint': 'Zeigt Bahnhofs-/Flughafennamen auf der Karte. Wenn aus, wird nur das Icon angezeigt.',

shared/src/i18n/en/settings.ts

@@ -53,6 +53,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Auto',
   'settings.language': 'Language',
   'settings.temperature': 'Temperature Unit',
+  'settings.distance': 'Distance Unit',
   'settings.timeFormat': 'Time Format',
   'settings.bookingLabels': 'Booking route labels',
   'settings.bookingLabelsHint': 'Show station / airport names on the map. When off, only the icon is shown.',

shared/src/i18n/es/settings.ts

@@ -55,6 +55,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automático',
   'settings.language': 'Idioma',
   'settings.temperature': 'Unidad de temperatura',
+  'settings.distance': 'Unidad de distancia',
   'settings.timeFormat': 'Formato de hora',
   'settings.blurBookingCodes': 'Difuminar códigos de reserva',
   'settings.optimizeFromAccommodation': 'Optimizar la ruta desde el alojamiento',

shared/src/i18n/fr/settings.ts

@@ -56,6 +56,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Auto',
   'settings.language': 'Langue',
   'settings.temperature': 'Unité de température',
+  'settings.distance': 'Unité de distance',
   'settings.timeFormat': "Format de l'heure",
   'settings.blurBookingCodes': 'Masquer les codes de réservation',
   'settings.optimizeFromAccommodation': "Optimiser l'itinéraire depuis l'hébergement",

shared/src/i18n/gr/settings.ts

@@ -57,6 +57,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Αυτόματο',
   'settings.language': 'Γλώσσα',
   'settings.temperature': 'Μονάδα Θερμοκρασίας',
+  'settings.distance': 'Μονάδα Απόστασης',
   'settings.timeFormat': 'Μορφή Ώρας',
   'settings.bookingLabels': 'Ετικέτες διαδρομής κρατήσεων',
   'settings.bookingLabelsHint':

shared/src/i18n/hu/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatikus',
   'settings.language': 'Nyelv',
   'settings.temperature': 'Hőmérséklet egység',
+  'settings.distance': 'Távolság egység',
   'settings.timeFormat': 'Időformátum',
   'settings.blurBookingCodes': 'Foglalási kódok elrejtése',
   'settings.optimizeFromAccommodation': 'Útvonal optimalizálása a szállástól',

shared/src/i18n/id/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Otomatis',
   'settings.language': 'Bahasa',
   'settings.temperature': 'Satuan Suhu',
+  'settings.distance': 'Satuan Jarak',
   'settings.timeFormat': 'Format Waktu',
   'settings.blurBookingCodes': 'Sembunyikan Kode Pemesanan',
   'settings.optimizeFromAccommodation': 'Optimalkan rute dari akomodasi',

shared/src/i18n/it/settings.ts

@@ -55,6 +55,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatica',
   'settings.language': 'Lingua',
   'settings.temperature': 'Unità di Temperatura',
+  'settings.distance': 'Unità di Distanza',
   'settings.timeFormat': 'Formato Ora',
   'settings.blurBookingCodes': 'Nascondi codici di prenotazione',
   'settings.optimizeFromAccommodation': "Ottimizza il percorso dall'alloggio",

shared/src/i18n/ja/settings.ts

@@ -52,6 +52,7 @@ const settings: TranslationStrings = {
   'settings.auto': '自動',
   'settings.language': '言語',
   'settings.temperature': '温度単位',
+  'settings.distance': '距離単位',
   'settings.timeFormat': '時刻形式',
   'settings.bookingLabels': '予約ルートのラベル',
   'settings.bookingLabelsHint': '地図に駅・空港名を表示。オフ時はアイコンのみ。',

shared/src/i18n/ko/settings.ts

@@ -53,6 +53,7 @@ const settings: TranslationStrings = {
   'settings.auto': '자동',
   'settings.language': '언어',
   'settings.temperature': '온도 단위',
+  'settings.distance': '거리 단위',
   'settings.timeFormat': '시간 형식',
   'settings.bookingLabels': '예약 경로 레이블',
   'settings.bookingLabelsHint': '지도에 역 / 공항 이름을 표시합니다. 끄면 아이콘만 표시됩니다.',

shared/src/i18n/nl/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatisch',
   'settings.language': 'Taal',
   'settings.temperature': 'Temperatuureenheid',
+  'settings.distance': 'Afstandseenheid',
   'settings.timeFormat': 'Tijdnotatie',
   'settings.blurBookingCodes': 'Boekingscodes vervagen',
   'settings.optimizeFromAccommodation': 'Route optimaliseren vanaf accommodatie',

shared/src/i18n/pl/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Automatyczny',
   'settings.language': 'Język',
   'settings.temperature': 'Jednostka temperatury',
+  'settings.distance': 'Jednostka odległości',
   'settings.timeFormat': 'Format czasu',
   'settings.blurBookingCodes': 'Rozmyj kody rezerwacji',
   'settings.optimizeFromAccommodation': 'Optymalizuj trasę od zakwaterowania',

shared/src/i18n/ru/settings.ts

@@ -53,6 +53,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Авто',
   'settings.language': 'Язык',
   'settings.temperature': 'Единица температуры',
+  'settings.distance': 'Единица расстояния',
   'settings.timeFormat': 'Формат времени',
   'settings.blurBookingCodes': 'Скрыть коды бронирования',
   'settings.optimizeFromAccommodation': 'Оптимизировать маршрут от места проживания',

shared/src/i18n/tr/settings.ts

@@ -53,6 +53,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Otomatik',
   'settings.language': 'Dil',
   'settings.temperature': 'Sıcaklık Birimi',
+  'settings.distance': 'Mesafe Birimi',
   'settings.timeFormat': 'Saat Biçimi',
   'settings.bookingLabels': 'Rezervasyon rota etiketleri',
   'settings.bookingLabelsHint': 'Haritada istasyon / havalimanı adlarını göster. Kapalıyken yalnızca simge görünür.',

shared/src/i18n/uk/settings.ts

@@ -54,6 +54,7 @@ const settings: TranslationStrings = {
   'settings.auto': 'Авто',
   'settings.language': 'Мова',
   'settings.temperature': 'Одиниця температури',
+  'settings.distance': 'Одиниця відстані',
   'settings.timeFormat': 'Формат часу',
   'settings.blurBookingCodes': 'Приховати коди бронювання',
   'settings.optimizeFromAccommodation': 'Оптимізувати маршрут від житла',

shared/src/i18n/zh-TW/settings.ts

@@ -52,6 +52,7 @@ const settings: TranslationStrings = {
   'settings.auto': '自動',
   'settings.language': '語言',
   'settings.temperature': '溫度單位',
+  'settings.distance': '距離單位',
   'settings.timeFormat': '時間格式',
   'settings.blurBookingCodes': '模糊預訂程式碼',
   'settings.optimizeFromAccommodation': '從住宿地點最佳化路線',

shared/src/i18n/zh/settings.ts

@@ -52,6 +52,7 @@ const settings: TranslationStrings = {
   'settings.auto': '自动',
   'settings.language': '语言',
   'settings.temperature': '温度单位',
+  'settings.distance': '距离单位',
   'settings.timeFormat': '时间格式',
   'settings.blurBookingCodes': '模糊预订代码',
   'settings.optimizeFromAccommodation': '从住宿地优化路线',