📦 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/no-nodejs-modules.md

@@ -0,0 +1,42 @@
+# import/no-nodejs-modules
+
+<!-- end auto-generated rule header -->
+
+Forbid the use of Node.js builtin modules. Can be useful for client-side web projects that do not have access to those modules.
+
+## Options
+
+This rule supports the following options:
+
+ - `allow`: Array of names of allowed modules. Defaults to an empty array.
+
+## Rule Details
+
+### Fail
+
+```js
+import fs from 'fs';
+import path from 'path';
+
+var fs = require('fs');
+var path = require('path');
+```
+
+### Pass
+
+```js
+import _ from 'lodash';
+import foo from 'foo';
+import foo from './foo';
+
+var _ = require('lodash');
+var foo = require('foo');
+var foo = require('./foo');
+
+/* eslint import/no-nodejs-modules: ["error", {"allow": ["path"]}] */
+import path from 'path';
+```
+
+## When Not To Use It
+
+If you have a project that is run mainly or partially using Node.js.