📦 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/own-keys/index.js

@@ -0,0 +1,21 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var safePushApply = require('safe-push-apply');
+
+var $ownKeys = GetIntrinsic('%Reflect.ownKeys%', true);
+var $gOPN = GetIntrinsic('%Object.getOwnPropertyNames%', true);
+var $gOPS = GetIntrinsic('%Object.getOwnPropertySymbols%', true);
+
+var keys = require('object-keys');
+
+/** @type {import('.')} */
+module.exports = $ownKeys || function ownKeys(source) {
+	/** @type {(keyof typeof source)[]} */
+	var sourceKeys = ($gOPN || keys)(source);
+	if ($gOPS) {
+		safePushApply(sourceKeys, $gOPS(source));
+	}
+	return sourceKeys;
+};