feat: add i18n infrastructure and language selector

Co-authored-by: Wikid82 <176516789+Wikid82@users.noreply.github.com>

frontend/src/context/LanguageContext.tsx

@@ -0,0 +1,30 @@
+import { ReactNode, useState, useEffect } from 'react'
+import { useTranslation } from 'react-i18next'
+import { LanguageContext, Language } from './LanguageContextValue'
+
+export function LanguageProvider({ children }: { children: ReactNode }) {
+  const { i18n } = useTranslation()
+  const [language, setLanguageState] = useState<Language>(() => {
+    const saved = localStorage.getItem('charon-language')
+    return (saved as Language) || 'en'
+  })
+
+  useEffect(() => {
+    i18n.changeLanguage(language)
+  }, [language, i18n])
+
+  const setLanguage = (lang: Language) => {
+    setLanguageState(lang)
+    localStorage.setItem('charon-language', lang)
+    i18n.changeLanguage(lang)
+    // Future: Update document direction for RTL languages (e.g., Arabic, Hebrew)
+    // Currently not used as we don't have RTL language translations yet
+    document.documentElement.dir = 'ltr'
+  }
+
+  return (
+    <LanguageContext.Provider value={{ language, setLanguage }}>
+      {children}
+    </LanguageContext.Provider>
+  )
+}