📦 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/is-generator-function/index.js

@@ -0,0 +1,31 @@
+'use strict';
+
+var callBound = require('call-bound');
+var safeRegexTest = require('safe-regex-test');
+var isFnRegex = safeRegexTest(/^\s*(?:function)?\*/);
+var hasToStringTag = require('has-tostringtag/shams')();
+var getProto = require('get-proto');
+
+var toStr = callBound('Object.prototype.toString');
+var fnToStr = callBound('Function.prototype.toString');
+
+var getGeneratorFunction = require('generator-function');
+
+/** @type {import('.')} */
+module.exports = function isGeneratorFunction(fn) {
+	if (typeof fn !== 'function') {
+		return false;
+	}
+	if (isFnRegex(fnToStr(fn))) {
+		return true;
+	}
+	if (!hasToStringTag) {
+		var str = toStr(fn);
+		return str === '[object GeneratorFunction]';
+	}
+	if (!getProto) {
+		return false;
+	}
+	var GeneratorFunction = getGeneratorFunction();
+	return GeneratorFunction && getProto(fn) === GeneratorFunction.prototype;
+};