📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/react-dom/README.md

@@ -0,0 +1,60 @@
+# `react-dom`
+
+This package serves as the entry point to the DOM and server renderers for React. It is intended to be paired with the generic React package, which is shipped as `react` to npm.
+
+## Installation
+
+```sh
+npm install react react-dom
+```
+
+## Usage
+
+### In the browser
+
+```js
+import { createRoot } from 'react-dom/client';
+
+function App() {
+  return <div>Hello World</div>;
+}
+
+const root = createRoot(document.getElementById('root'));
+root.render(<App />);
+```
+
+### On the server
+
+```js
+import { renderToPipeableStream } from 'react-dom/server';
+
+function App() {
+  return <div>Hello World</div>;
+}
+
+function handleRequest(res) {
+  // ... in your server handler ...
+  const stream = renderToPipeableStream(<App />, {
+    onShellReady() {
+      res.statusCode = 200;
+      res.setHeader('Content-type', 'text/html');
+      stream.pipe(res);
+    },
+    // ...
+  });
+}
+```
+
+## API
+
+### `react-dom`
+
+See https://reactjs.org/docs/react-dom.html
+
+### `react-dom/client`
+
+See https://reactjs.org/docs/react-dom-client.html
+
+### `react-dom/server`
+
+See https://reactjs.org/docs/react-dom-server.html