🩹(frontend) use browser language if no localStorage for detection

Previously, language detection was failing to read browser settings correctly.
Added explicit detection order to ensure localStorage preferences are checked
before falling back to browser language.

src/frontend/src/i18n/init.ts

@@ -13,11 +13,14 @@ i18n
   )
   .use(initReactI18next)
   .use(LanguageDetector)
-i18n.init({
-  supportedLngs: ['en', 'fr'],
-  fallbackLng: 'en',
-  ns: i18nDefaultNamespace,
-  interpolation: {
-    escapeValue: false,
-  },
-})
+  .init({
+    supportedLngs: ['en', 'fr'],
+    fallbackLng: 'fr',
+    ns: i18nDefaultNamespace,
+    detection: {
+      order: ['localStorage', 'navigator'],
+    },
+    interpolation: {
+      escapeValue: false,
+    },
+  })