Refactor language name mapping for better maintainability

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

apps/docs/app/[lang]/layout.tsx

@@ -2,6 +2,12 @@ import type { ReactNode } from 'react';
 import { RootProvider } from 'fumadocs-ui/provider/next';
 import { i18n } from '@/lib/i18n';
 
+// Language display names mapping
+const LANGUAGE_NAMES: Record<string, string> = {
+  en: 'English',
+  cn: '中文',
+};
+
 export default async function LanguageLayout({
   params,
   children,
@@ -18,7 +24,7 @@ export default async function LanguageLayout({
           i18n={{
             locale: lang,
             locales: i18n.languages.map((l) => ({
-              name: l === 'en' ? 'English' : '中文',
+              name: LANGUAGE_NAMES[l] || l,
               locale: l,
             })),
           }}