feat(frontend): Markdown 支持 GFM、代码高亮与图片灯箱

统一 SSR/客户端渲染路径，评论与预览共用增强组件。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/components/MarkdownBody.tsx

@@ -1,4 +1,5 @@
-import ReactMarkdown, { type Components } from "react-markdown";
+import type { Components } from "react-markdown";
+import { renderMarkdownToReact } from "@/components/markdown/renderMarkdown";
 
 type MarkdownBodyProps = {
   content: string;
@@ -6,15 +7,15 @@ type MarkdownBodyProps = {
   components?: Components;
 };
 
-/** 站点统一 Markdown 渲染：详情页 / 发帖预览共用 prose-content */
-export default function MarkdownBody({
+/**
+ * 站点统一 Markdown 渲染（服务端）：GFM + Shiki 双主题、图箱、代码块复制/折叠。
+ * 客户端预览请用 MarkdownBodyClient。
+ */
+export default async function MarkdownBody({
   content,
   className = "prose-content",
   components,
 }: MarkdownBodyProps) {
-  return (
-    <div className={className}>
-      <ReactMarkdown components={components}>{content || ""}</ReactMarkdown>
-    </div>
-  );
+  const tree = await renderMarkdownToReact(content, components);
+  return <div className={className}>{tree}</div>;
 }