📦 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-abstract/2017/AbstractRelationalComparison.js

@@ -0,0 +1,62 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $Number = GetIntrinsic('%Number%');
+var $TypeError = require('es-errors/type');
+var $isNaN = require('math-intrinsics/isNaN');
+var $isFinite = require('math-intrinsics/isFinite');
+
+var isPrefixOf = require('../helpers/isPrefixOf');
+
+var ToNumber = require('./ToNumber');
+var ToPrimitive = require('./ToPrimitive');
+
+// https://262.ecma-international.org/5.1/#sec-11.8.5
+
+// eslint-disable-next-line max-statements
+module.exports = function AbstractRelationalComparison(x, y, LeftFirst) {
+	if (typeof LeftFirst !== 'boolean') {
+		throw new $TypeError('Assertion failed: LeftFirst argument must be a Boolean');
+	}
+	var px;
+	var py;
+	if (LeftFirst) {
+		px = ToPrimitive(x, $Number);
+		py = ToPrimitive(y, $Number);
+	} else {
+		py = ToPrimitive(y, $Number);
+		px = ToPrimitive(x, $Number);
+	}
+	var bothStrings = typeof px === 'string' && typeof py === 'string';
+	if (!bothStrings) {
+		var nx = ToNumber(px);
+		var ny = ToNumber(py);
+		if ($isNaN(nx) || $isNaN(ny)) {
+			return undefined;
+		}
+		if ($isFinite(nx) && $isFinite(ny) && nx === ny) {
+			return false;
+		}
+		if (nx === Infinity) {
+			return false;
+		}
+		if (ny === Infinity) {
+			return true;
+		}
+		if (ny === -Infinity) {
+			return false;
+		}
+		if (nx === -Infinity) {
+			return true;
+		}
+		return nx < ny; // by now, these are both nonzero, finite, and not equal
+	}
+	if (isPrefixOf(py, px)) {
+		return false;
+	}
+	if (isPrefixOf(px, py)) {
+		return true;
+	}
+	return px < py; // both strings, neither a prefix of the other. shortcut for steps c-f
+};