📦 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/eslint-plugin-import/docs/rules/export.md

@@ -0,0 +1,37 @@
+# import/export
+
+💼 This rule is enabled in the following configs: ❗ `errors`, ☑️ `recommended`.
+
+<!-- end auto-generated rule header -->
+
+Reports funny business with exports, like repeated exports of names or defaults.
+
+## Rule Details
+
+```js
+export default class MyClass { /*...*/ } // Multiple default exports.
+
+function makeClass() { return new MyClass(...arguments) }
+
+export default makeClass // Multiple default exports.
+```
+
+or
+
+```js
+export const foo = function () { /*...*/ } // Multiple exports of name 'foo'.
+
+function bar() { /*...*/ }
+export { bar as foo } // Multiple exports of name 'foo'.
+```
+
+In the case of named/default re-export, all `n` re-exports will be reported,
+as at least `n-1` of them are clearly mistakes, but it is not clear which one
+(if any) is intended. Could be the result of copy/paste, code duplication with
+intent to rename, etc.
+
+## Further Reading
+
+ - Lee Byron's [ES7] export proposal
+
+[ES7]: https://github.com/leebyron/ecmascript-more-export-from