📦 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/for-each/README.md

@@ -0,0 +1,39 @@
+# for-each [![build status][1]][2]
+
+[![browser support][3]][4]
+
+A better forEach.
+
+## Example
+
+Like `Array.prototype.forEach` but works on objects.
+
+```js
+var forEach = require("for-each")
+
+forEach({ key: "value" }, function (value, key, object) {
+    /* code */
+})
+```
+
+As a bonus, it's also a perfectly function shim/polyfill for arrays too!
+
+```js
+var forEach = require("for-each")
+
+forEach([1, 2, 3], function (value, index, array) {
+    /* code */
+})
+```
+
+## Installation
+
+`npm install for-each`
+
+## MIT Licenced
+
+  [1]: https://secure.travis-ci.org/Raynos/for-each.png
+  [2]: http://travis-ci.org/Raynos/for-each
+  [3]: https://ci.testling.com/Raynos/for-each.png
+  [4]: https://ci.testling.com/Raynos/for-each
+