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/package.json

@@ -7,7 +7,7 @@
     "build": "next build",
     "start": "next start -p 3000",
     "lint": "next lint",
-    "test": "node --experimental-strip-types --test lib/siteUrl.test.ts lib/jsonLd.test.ts lib/urlStyle.test.ts lib/widgetCode.test.ts lib/smartDiff.test.ts"
+    "test": "node --experimental-strip-types --test lib/siteUrl.test.ts lib/jsonLd.test.ts lib/urlStyle.test.ts lib/widgetCode.test.ts lib/smartDiff.test.ts lib/dyEmoji.test.ts"
   },
   "dependencies": {
     "hast-util-to-jsx-runtime": "^2.3.6",