feat(I18n) 添加I18n相关功能，支持中文和英文

src/client/App.tsx

@@ -1,5 +1,6 @@
 import { useState, useCallback } from 'react'
 import { ThemeProvider } from './contexts/ThemeContext'
+import { LanguageProvider, useLanguage } from './contexts/LanguageContext'
 import FloatingHeader from './components/FloatingHeader'
 import IpInput from './components/IpInput'
 import LatencyMap from './components/LatencyMap'
@@ -12,6 +13,7 @@ function AppContent() {
   const [results, setResults] = useState<Map<string, LatencyResult>>(new Map())
   const [testing, setTesting] = useState(false)
   const [selectedNodeId, setSelectedNodeId] = useState<string | null>(null)
+  const { t } = useLanguage()
 
   const handleTest = useCallback(async (target: string) => {
     setTesting(true)
@@ -35,7 +37,7 @@ function AppContent() {
 
       <main className="app-main" style={{ paddingTop: '5rem' }}>
         <p className="app-description">
-          Test network latency from global locations to any IP address or domain
+          {t('从全球各地测试到任意IP地址或域名的网络延迟', 'Test network latency from global locations to any IP address or domain')}
         </p>
         <IpInput onTest={handleTest} testing={testing} />
         <LatencyMap
@@ -51,7 +53,7 @@ function AppContent() {
       </main>
 
       <footer className="app-footer">
-        <p>© 2024 Latency Test. Powered by GlobalPing.</p>
+        <p>{t('© 2024 延迟测试。由 GlobalPing 提供支持。', '© 2024 Latency Test. Powered by GlobalPing.')}</p>
       </footer>
     </div>
   )
@@ -60,7 +62,9 @@ function AppContent() {
 export default function App() {
   return (
     <ThemeProvider>
-      <AppContent />
+      <LanguageProvider>
+        <AppContent />
+      </LanguageProvider>
     </ThemeProvider>
   )
 }