📦 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/postcss-minify-params/README.md

@@ -0,0 +1,39 @@
+# postcss-minify-params [![Build Status][ci-img]][ci]
+
+> Minify at-rule params with PostCSS.
+
+```css
+@media only screen   and ( min-width: 400px, min-height: 500px ) {
+    h2{
+        color:blue
+    }
+}
+```
+
+```css
+@media only screen and (min-width:400px,min-height:500px) {
+    h2{
+        color:blue
+    }
+}
+```
+
+## Usage
+
+```js
+postcss([ require('postcss-minify-params') ])
+```
+
+See [PostCSS] docs for examples for your environment.
+
+## Contributors
+
+See [CONTRIBUTORS.md](https://github.com/cssnano/cssnano/blob/master/CONTRIBUTORS.md).
+
+## License
+
+MIT © [Bogdan Chadkin](mailto:trysound@yandex.ru)
+
+[PostCSS]: https://github.com/postcss/postcss
+[ci-img]:  https://travis-ci.org/cssnano/postcss-minify-params.svg
+[ci]:      https://travis-ci.org/cssnano/postcss-minify-params