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/open-next.config.ts

@@ -0,0 +1,4 @@
+import { defineCloudflareConfig } from '@opennextjs/cloudflare';
+
+// 站点全部页面在构建期静态生成，无需增量缓存 / 队列等运行时缓存设施。
+export default defineCloudflareConfig({});