feat: add LocaleProvider and hooks for managing locale and timezone settings

src/App.tsx

@@ -1,4 +1,5 @@
 import { Navigate, Route, Routes } from 'react-router'
+import { LocaleProvider } from './components/LocaleProvider'
 import { ThemeProvider } from './components/ThemeProvider'
 import { Toaster } from './components/ui/sonner'
 import { AuthProvider, useAuth } from './contexts/AuthContext'
@@ -139,14 +140,16 @@ function AppRoutes() {
 
 function App() {
   return (
-    <ThemeProvider defaultTheme="dark" storageKey="vite-ui-theme">
-      <AuthProvider>
-        <SocketProvider>
-          <AppRoutes />
-          <Toaster richColors />
-        </SocketProvider>
-      </AuthProvider>
-    </ThemeProvider>
+    <LocaleProvider defaultLocale="fr-FR" defaultTimezone="Europe/Paris">
+      <ThemeProvider defaultTheme="dark" storageKey="vite-ui-theme">
+        <AuthProvider>
+          <SocketProvider>
+            <AppRoutes />
+            <Toaster richColors />
+          </SocketProvider>
+        </AuthProvider>
+      </ThemeProvider>
+    </LocaleProvider>
   )
 }
 

src/components/LocaleProvider.tsx

@@ -0,0 +1,70 @@
+import { type Locale, LocaleProviderContext } from '@/contexts/LocaleContext'
+import { getSupportedTimezones } from '@/lib/utils/locale'
+import { useEffect, useState } from 'react'
+
+type LocaleProviderProps = {
+  children: React.ReactNode
+  defaultLocale?: Locale
+  defaultTimezone?: string
+  localeStorageKey?: string
+  timezoneStorageKey?: string
+}
+
+export function LocaleProvider({
+  children,
+  defaultLocale = 'fr-FR',
+  defaultTimezone = 'Europe/Paris',
+  localeStorageKey = 'locale',
+  timezoneStorageKey = 'timezone',
+  ...props
+}: LocaleProviderProps) {
+  const [locale, setLocaleState] = useState<Locale>(() => {
+    const stored = localStorage.getItem(localeStorageKey) as Locale
+    const validLocale = stored && ['en-US', 'fr-FR'].includes(stored) ? stored : defaultLocale
+    
+    // Set default in localStorage if not present
+    if (!stored) {
+      localStorage.setItem(localeStorageKey, defaultLocale)
+    }
+    
+    return validLocale
+  })
+
+  const [timezone, setTimezoneState] = useState<string>(() => {
+    const stored = localStorage.getItem(timezoneStorageKey)
+    const supportedTimezones = getSupportedTimezones()
+    const validTimezone = stored && supportedTimezones.includes(stored) ? stored : defaultTimezone
+    
+    // Set default in localStorage if not present
+    if (!stored) {
+      localStorage.setItem(timezoneStorageKey, defaultTimezone)
+    }
+    
+    return validTimezone
+  })
+
+  useEffect(() => {
+    // Set document language attribute for accessibility
+    document.documentElement.lang = locale.split('-')[0]
+  }, [locale])
+
+  const value = {
+    locale,
+    timezone,
+    setLocale: (newLocale: Locale) => {
+      localStorage.setItem(localeStorageKey, newLocale)
+      setLocaleState(newLocale)
+    },
+    setTimezone: (newTimezone: string) => {
+      localStorage.setItem(timezoneStorageKey, newTimezone)
+      setTimezoneState(newTimezone)
+    },
+  }
+
+  return (
+    <LocaleProviderContext.Provider {...props} value={value}>
+      {children}
+    </LocaleProviderContext.Provider>
+  )
+}
+

src/contexts/LocaleContext.tsx

@@ -0,0 +1,21 @@
+import { createContext } from 'react'
+
+type Locale = 'en-US' | 'fr-FR'
+
+type LocaleProviderState = {
+  locale: Locale
+  timezone: string
+  setLocale: (locale: Locale) => void
+  setTimezone: (timezone: string) => void
+}
+
+const initialState: LocaleProviderState = {
+  locale: 'fr-FR',
+  timezone: 'Europe/Paris',
+  setLocale: () => null,
+  setTimezone: () => null,
+}
+
+export const LocaleProviderContext =
+  createContext<LocaleProviderState>(initialState)
+export type { Locale, LocaleProviderState }

src/hooks/use-locale.ts

@@ -0,0 +1,11 @@
+import { LocaleProviderContext } from '@/contexts/LocaleContext'
+import { useContext } from 'react'
+
+export const useLocale = () => {
+  const context = useContext(LocaleProviderContext)
+
+  if (context === undefined)
+    throw new Error('useLocale must be used within a LocaleProvider')
+
+  return context
+}

src/lib/utils/locale.ts

@@ -0,0 +1,14 @@
+// Get supported timezones, fallback to basic list if Intl.supportedValuesOf is not available
+export const getSupportedTimezones = (): string[] => {
+  try {
+    if (typeof Intl !== 'undefined' && 'supportedValuesOf' in Intl) {
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      return (Intl as any).supportedValuesOf('timeZone')
+    }
+  } catch {
+    console.warn('Intl.supportedValuesOf not available, using fallback timezones')
+  }
+  
+  // Fallback timezone list
+  return ['America/New_York', 'Europe/Paris']
+}

src/pages/AccountPage.tsx

@@ -20,6 +20,8 @@ import {
 import { Skeleton } from '@/components/ui/skeleton'
 import { useAuth } from '@/contexts/AuthContext'
 import { useTheme } from '@/hooks/use-theme'
+import { useLocale } from '@/hooks/use-locale'
+import { getSupportedTimezones } from '@/lib/utils/locale'
 import {
   type ApiTokenStatusResponse,
   type UserProvider,
@@ -44,6 +46,7 @@ import { toast } from 'sonner'
 export function AccountPage() {
   const { user, setUser } = useAuth()
   const { theme, setTheme } = useTheme()
+  const { locale, timezone, setLocale, setTimezone } = useLocale()
 
   // Profile state
   const [profileName, setProfileName] = useState('')
@@ -363,11 +366,62 @@ export function AccountPage() {
                 </p>
               </div>
 
-              <div className="pt-4">
+              <div className="space-y-2">
+                <Label>Language Preference</Label>
+                <Select
+                  value={locale}
+                  onValueChange={(value: 'en-US' | 'fr-FR') =>
+                    setLocale(value)
+                  }
+                >
+                  <SelectTrigger>
+                    <SelectValue />
+                  </SelectTrigger>
+                  <SelectContent>
+                    <SelectItem value="en-US">English (US)</SelectItem>
+                    <SelectItem value="fr-FR">Français (FR)</SelectItem>
+                  </SelectContent>
+                </Select>
+                <p className="text-xs text-muted-foreground">
+                  Choose your preferred language for the interface
+                </p>
+              </div>
+
+              <div className="space-y-2">
+                <Label>Timezone</Label>
+                <Select
+                  value={timezone}
+                  onValueChange={setTimezone}
+                >
+                  <SelectTrigger>
+                    <SelectValue />
+                  </SelectTrigger>
+                  <SelectContent>
+                    {getSupportedTimezones().map((tz) => (
+                      <SelectItem key={tz} value={tz}>
+                        {tz.replace('_', ' ')}
+                      </SelectItem>
+                    ))}
+                  </SelectContent>
+                </Select>
+                <p className="text-xs text-muted-foreground">
+                  Choose your timezone for date and time display
+                </p>
+              </div>
+
+              <div className="pt-4 space-y-1">
                 <div className="text-sm text-muted-foreground">
                   Current theme:{' '}
                   <span className="font-medium capitalize">{theme}</span>
                 </div>
+                <div className="text-sm text-muted-foreground">
+                  Current language:{' '}
+                  <span className="font-medium">{locale === 'en-US' ? 'English (US)' : 'Français (FR)'}</span>
+                </div>
+                <div className="text-sm text-muted-foreground">
+                  Current timezone:{' '}
+                  <span className="font-medium">{timezone.replace('_', ' ')}</span>
+                </div>
               </div>
             </CardContent>
           </Card>