📦 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/is-fullwidth-code-point/readme.md

@@ -0,0 +1,39 @@
+# is-fullwidth-code-point [![Build Status](https://travis-ci.org/sindresorhus/is-fullwidth-code-point.svg?branch=master)](https://travis-ci.org/sindresorhus/is-fullwidth-code-point)
+
+> Check if the character represented by a given [Unicode code point](https://en.wikipedia.org/wiki/Code_point) is [fullwidth](https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms)
+
+
+## Install
+
+```
+$ npm install is-fullwidth-code-point
+```
+
+
+## Usage
+
+```js
+const isFullwidthCodePoint = require('is-fullwidth-code-point');
+
+isFullwidthCodePoint('谢'.codePointAt(0));
+//=> true
+
+isFullwidthCodePoint('a'.codePointAt(0));
+//=> false
+```
+
+
+## API
+
+### isFullwidthCodePoint(codePoint)
+
+#### codePoint
+
+Type: `number`
+
+The [code point](https://en.wikipedia.org/wiki/Code_point) of a character.
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)