Add documents site (#1767)

* feat: add docs site

- Implemented dynamic routing for MDX documentation pages with language support.
- Created layout components for documentation with a header and footer.
- Added metadata for various documentation sections in English and Chinese.
- Developed initial content for the DeerFlow App and Harness documentation.
- Introduced i18n hooks and translations for English and Chinese languages.
- Enhanced header component to include navigation links for documentation and blog.
- Established a structure for tutorials and reference materials.
- Created a new translations file to manage locale-specific strings.

* feat: enhance documentation structure and content for application and harness sections

* feat: update .gitignore to include .playwright-mcp and remove obsolete Playwright YAML file

* fix(docs): correct punctuation and formatting in documentation files

* feat(docs): remove outdated index.mdx file from documentation

* fix(docs): update documentation links and improve Chinese description in index.mdx

* fix(docs): update title in Chinese for meta information in _meta.ts

frontend/src/components/landing/header.tsx

@@ -1,21 +1,54 @@
 import { StarFilledIcon, GitHubLogoIcon } from "@radix-ui/react-icons";
+import Link from "next/link";
 
 import { Button } from "@/components/ui/button";
 import { NumberTicker } from "@/components/ui/number-ticker";
+import type { Locale } from "@/core/i18n/locale";
+import { getI18n } from "@/core/i18n/server";
 import { env } from "@/env";
+import { cn } from "@/lib/utils";
 
-export function Header() {
+export type HeaderProps = {
+  className?: string;
+  homeURL?: string;
+  locale?: Locale;
+};
+
+export async function Header({ className, homeURL, locale }: HeaderProps) {
+  const isExternalHome = !homeURL;
+  const { locale: resolvedLocale, t } = await getI18n(locale);
+  const lang = resolvedLocale.substring(0, 2);
   return (
-    <header className="container-md fixed top-0 right-0 left-0 z-20 mx-auto flex h-16 items-center justify-between backdrop-blur-xs">
-      <div className="flex items-center gap-2">
+    <header
+      className={cn(
+        "container-md fixed top-0 right-0 left-0 z-20 mx-auto flex h-16 items-center justify-between backdrop-blur-xs",
+        className,
+      )}
+    >
+      <div className="flex items-center gap-6">
         <a
-          href="https://github.com/bytedance/deer-flow"
-          target="_blank"
-          rel="noopener noreferrer"
+          href={homeURL ?? "https://github.com/bytedance/deer-flow"}
+          target={isExternalHome ? "_blank" : "_self"}
+          rel={isExternalHome ? "noopener noreferrer" : undefined}
         >
           <h1 className="font-serif text-xl">DeerFlow</h1>
         </a>
       </div>
+      <nav className="mr-8 ml-auto flex items-center gap-8 text-sm font-medium">
+        <Link
+          href={`/${lang}/docs`}
+          className="text-secondary-foreground hover:text-foreground transition-colors"
+        >
+          {t.home.docs}
+        </Link>
+        <a
+          href={`/${lang}/blog`}
+          target="_self"
+          className="text-secondary-foreground hover:text-foreground transition-colors"
+        >
+          {t.home.blog}
+        </a>
+      </nav>
       <div className="relative">
         <div
           className="pointer-events-none absolute inset-0 z-0 h-full w-full rounded-full opacity-30 blur-2xl"