feat(docs): enhance documentation site with internationalization and layout updates

- Updated the demo API to support locale-based content rendering.
- Refactored the main layout to accommodate language-specific metadata and routing.
- Introduced new components for blog and documentation pages, ensuring proper language handling.
- Added styles for improved UI consistency across different sections.
- Removed deprecated layout files and streamlined the structure for better maintainability.

apps/docs/components/hero/DownloadButton.tsx

@@ -0,0 +1,37 @@
+'use client';
+
+import { useSyncExternalStore } from 'react';
+import { Download } from 'lucide-react';
+import type { Language } from '@/lib/i18n';
+import { releaseUrl } from '@/lib/shared';
+
+function detectPlatform(): string | null {
+  const ua = navigator.userAgent;
+  if (/Mac/i.test(ua)) return 'macOS';
+  if (/Win/i.test(ua)) return 'Windows';
+  if (/Linux|X11/i.test(ua)) return 'Linux';
+  return null;
+}
+
+const labels: Record<Language, { platform: (platform: string) => string; fallback: string }> = {
+  zh: { platform: (platform) => `下载 ${platform} 版`, fallback: '下载最新版' },
+  en: { platform: (platform) => `Download for ${platform}`, fallback: 'Download' },
+};
+
+const subscribeNoop = () => () => {};
+
+export function DownloadButton({ lang }: { lang: Language }) {
+  // 平台只在客户端可知；SSR 用通用文案，水合后替换为平台文案
+  const platform = useSyncExternalStore(subscribeNoop, detectPlatform, () => null);
+  const label = labels[lang];
+
+  return (
+    <a
+      href={releaseUrl}
+      className="inline-flex items-center gap-2 rounded-lg bg-fd-primary px-5 py-3 font-medium text-fd-primary-foreground transition-opacity hover:opacity-90"
+    >
+      <Download className="size-4" />
+      {platform ? label.platform(platform) : label.fallback}
+    </a>
+  );
+}