📦 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/@pmmmwh/react-refresh-webpack-plugin/lib/utils/index.js

@@ -0,0 +1,19 @@
+const getAdditionalEntries = require('./getAdditionalEntries');
+const getIntegrationEntry = require('./getIntegrationEntry');
+const getRefreshGlobal = require('./getRefreshGlobal');
+const getSocketIntegration = require('./getSocketIntegration');
+const injectRefreshEntry = require('./injectRefreshEntry');
+const injectRefreshLoader = require('./injectRefreshLoader');
+const makeRefreshRuntimeModule = require('./makeRefreshRuntimeModule');
+const normalizeOptions = require('./normalizeOptions');
+
+module.exports = {
+  getAdditionalEntries,
+  getIntegrationEntry,
+  getRefreshGlobal,
+  getSocketIntegration,
+  injectRefreshEntry,
+  injectRefreshLoader,
+  makeRefreshRuntimeModule,
+  normalizeOptions,
+};