📦 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/strip-final-newline/readme.md

@@ -0,0 +1,30 @@
+# strip-final-newline [![Build Status](https://travis-ci.com/sindresorhus/strip-final-newline.svg?branch=master)](https://travis-ci.com/sindresorhus/strip-final-newline)
+
+> Strip the final [newline character](https://en.wikipedia.org/wiki/Newline) from a string/buffer
+
+Can be useful when parsing the output of, for example, `ChildProcess#execFile`, as [binaries usually output a newline at the end](https://stackoverflow.com/questions/729692/why-should-text-files-end-with-a-newline). Normally, you would use `stdout.trim()`, but that would also remove newlines at the start and whitespace.
+
+
+## Install
+
+```
+$ npm install strip-final-newline
+```
+
+
+## Usage
+
+```js
+const stripFinalNewline = require('strip-final-newline');
+
+stripFinalNewline('foo\nbar\n\n');
+//=> 'foo\nbar\n'
+
+stripFinalNewline(Buffer.from('foo\nbar\n\n')).toString();
+//=> 'foo\nbar\n'
+```
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)