fix(chat): 修复暗黑模式下 Markdown 和滚动条样式 — 响应式 useIsDark hook + 动态主题切换

src/web/css.d.ts

@@ -1 +1,4 @@
 declare module "*.css";
+declare module "react-syntax-highlighter/dist/esm/styles/prism" {
+  export { oneDark, oneLight } from "react-syntax-highlighter";
+}