📦 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/es-iterator-helpers/Iterator/auto.js

@@ -0,0 +1,3 @@
+'use strict';
+
+require('./shim')();

frontend/node_modules/es-iterator-helpers/Iterator/implementation.js

@@ -0,0 +1,30 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+var hasPropertyDescriptors = require('has-property-descriptors')();
+
+var $TypeError = require('es-errors/type');
+
+var $defineProperty = hasPropertyDescriptors && GetIntrinsic('%Object.defineProperty%', true);
+
+var iterProto = require('iterator.prototype');
+var callBound = require('call-bound');
+
+var $isPrototypeOf = callBound('Object.prototype.isPrototypeOf');
+
+var $Iterator = typeof Iterator === 'function' ? Iterator : function Iterator() {
+	if (
+		!(this instanceof Iterator)
+		|| this.constructor === Iterator
+		|| !$isPrototypeOf(Iterator, this.constructor)
+	) {
+		throw new $TypeError('`Iterator` can not be called or constructed directly');
+	}
+};
+
+if ($Iterator.prototype !== iterProto) {
+	$Iterator.prototype = iterProto;
+}
+$defineProperty($Iterator, 'prototype', { writable: false });
+
+module.exports = $Iterator;

frontend/node_modules/es-iterator-helpers/Iterator/index.js

@@ -0,0 +1,18 @@
+'use strict';
+
+var define = require('define-properties');
+var callBind = require('call-bind');
+
+var implementation = require('./implementation');
+var getPolyfill = require('./polyfill');
+var shim = require('./shim');
+
+var polyfill = callBind(getPolyfill());
+
+define(polyfill, {
+	getPolyfill: getPolyfill,
+	implementation: implementation,
+	shim: shim
+});
+
+module.exports = polyfill;

frontend/node_modules/es-iterator-helpers/Iterator/polyfill.js

@@ -0,0 +1,8 @@
+'use strict';
+
+var globalThis = require('globalthis')();
+var implementation = require('./implementation');
+
+module.exports = function getPolyfill() {
+	return typeof globalThis.Iterator === 'function' ? globalThis.Iterator : implementation;
+};

frontend/node_modules/es-iterator-helpers/Iterator/shim.js

@@ -0,0 +1,18 @@
+'use strict';
+
+var define = require('define-properties');
+var globalThis = require('globalthis')();
+
+var getPolyfill = require('./polyfill');
+
+module.exports = function shimIterator() {
+	var polyfill = getPolyfill();
+
+	define(
+		globalThis,
+		{ Iterator: polyfill },
+		{ Iterator: function () { return Iterator !== polyfill; } }
+	);
+
+	return polyfill;
+};