feat(i18n): Enhance internationalization with dynamic locale management

- Add comprehensive locale management with `useLocale` composable
- Implement dynamic locale loading and persistent storage
- Create type-safe internationalization infrastructure
- Add flag emojis and locale selection utilities
- Expand English locale with more comprehensive message schemas

src/composables/useLocale.ts

@@ -0,0 +1,43 @@
+import { computed } from 'vue'
+import { useI18n } from 'vue-i18n'
+import type { AvailableLocale } from '@/i18n'
+import { AVAILABLE_LOCALES, changeLocale, isAvailableLocale } from '@/i18n'
+
+export function useLocale() {
+  const { locale, t } = useI18n()
+
+  const currentLocale = computed(() => locale.value as AvailableLocale)
+  
+  const locales = computed(() => 
+    AVAILABLE_LOCALES.map(code => ({
+      code,
+      name: t(`locales.${code}`),
+      flag: getFlagEmoji(code)
+    }))
+  )
+
+  async function setLocale(newLocale: string) {
+    if (isAvailableLocale(newLocale)) {
+      await changeLocale(newLocale)
+    }
+  }
+
+  // Helper function to get flag emoji from locale code
+  function getFlagEmoji(locale: string): string {
+    const flagMap: Record<string, string> = {
+      'en': '🇬🇧',
+      'es': '🇪🇸',
+      'fr': '🇫🇷',
+      'de': '🇩🇪',
+      'zh': '🇨🇳'
+    }
+    return flagMap[locale] || '🌐'
+  }
+
+  return {
+    currentLocale,
+    locales,
+    setLocale,
+    isAvailableLocale
+  }
+}