feat: 论坛 emoji 表情支持

- 新增 dyEmoji 表情库与解析测试、EmojiPicker 选择器与 EmojiImg 组件
- Markdown 编辑器/渲染支持表情图片，新增 public/emoji 资源与生成脚本
- 聊天室与首页适配

frontend/components/MarkdownBody.tsx

@@ -2,6 +2,7 @@ import type { ReactNode } from "react";
 import type { Components } from "react-markdown";
 import { renderMarkdownToReact } from "@/components/markdown/renderMarkdown";
 import { splitContentSegments } from "@/lib/directiveBlocks";
+import { expandDyEmojiShortcodes } from "@/lib/dyEmoji";
 import type { HideKind } from "@/lib/hideBlocks";
 import MdHideBlock from "@/components/markdown/MdHideBlock";
 import MdTimeline from "@/components/markdown/MdTimeline";
@@ -28,7 +29,7 @@ export default async function MarkdownBody({
   loginHref,
   loggedIn = false,
 }: MarkdownBodyProps) {
-  const segs = splitContentSegments(content || "");
+  const segs = splitContentSegments(expandDyEmojiShortcodes(content || ""));
   const nodes = [];
   for (let i = 0; i < segs.length; i++) {
     const seg = segs[i];
@@ -48,7 +49,7 @@ export default async function MarkdownBody({
           continue;
         }
         // 条目正文不挂目录 id，避免与块外 headingRenderer 错位
-        bodies.push(await renderMarkdownToReact(it.body));
+        bodies.push(await renderMarkdownToReact(expandDyEmojiShortcodes(it.body)));
       }
       nodes.push(
         <MdTimeline
@@ -75,7 +76,7 @@ export default async function MarkdownBody({
       continue;
     }
     const inner = seg.body.trim()
-      ? await renderMarkdownToReact(seg.body)
+      ? await renderMarkdownToReact(expandDyEmojiShortcodes(seg.body))
       : null;
     nodes.push(
       <MdHideBlock key={`hide-${i}`} kind={kind} points={seg.points}>