📦 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/acorn-import-phases/README.md

@@ -0,0 +1,30 @@
+# Support for `import defer` and `import souce` in acorn
+
+## Install
+
+```
+npm install acorn-import-phases
+```
+
+## Usage
+
+This module provides a plugin that can be used to extend the Acorn Parser class:
+
+```js
+const {Parser} = require('acorn');
+const importPhases = require('acorn-import-phases');
+Parser.extend(importPhases()).parse('...');
+```
+
+By default, the plugin supports both `import defer` and `import source` syntax. You can disable one of them by passing an options object:
+
+```js
+const {Parser} = require('acorn');
+const importPhases = require('acorn-import-phases');
+Parser.extend(importPhases({ defer: false })).parse('...');
+Parser.extend(importPhases({ source: false })).parse('...');
+```
+
+## License
+
+This plugin is released under an MIT License.