feat: 类型帖互动、积分经济与发帖体验

补齐问答采纳/重开、投票匿名与有票禁编、悬赏过期退回、抽奖回帖开奖，并接入积分账本与发帖附件可见性。

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

frontend/components/MarkdownBody.tsx

@@ -0,0 +1,20 @@
+import ReactMarkdown, { type Components } from "react-markdown";
+
+type MarkdownBodyProps = {
+  content: string;
+  className?: string;
+  components?: Components;
+};
+
+/** 站点统一 Markdown 渲染：详情页 / 发帖预览共用 prose-content */
+export default function MarkdownBody({
+  content,
+  className = "prose-content",
+  components,
+}: MarkdownBodyProps) {
+  return (
+    <div className={className}>
+      <ReactMarkdown components={components}>{content || ""}</ReactMarkdown>
+    </div>
+  );
+}