📦 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-negative-zero/test/index.js

@@ -0,0 +1,29 @@
+'use strict';
+
+var test = require('tape');
+var isNegativeZero = require('../');
+
+test('not negative zero', function (t) {
+	// @ts-expect-error
+	t.notOk(isNegativeZero(), 'undefined is not negative zero');
+	t.notOk(isNegativeZero(null), 'null is not negative zero');
+	t.notOk(isNegativeZero(false), 'false is not negative zero');
+	t.notOk(isNegativeZero(true), 'true is not negative zero');
+	t.notOk(isNegativeZero(0), 'positive zero is not negative zero');
+	t.notOk(isNegativeZero(Infinity), 'Infinity is not negative zero');
+	t.notOk(isNegativeZero(-Infinity), '-Infinity is not negative zero');
+	t.notOk(isNegativeZero(NaN), 'NaN is not negative zero');
+	t.notOk(isNegativeZero('foo'), 'string is not negative zero');
+	t.notOk(isNegativeZero([]), 'array is not negative zero');
+	t.notOk(isNegativeZero({}), 'object is not negative zero');
+	t.notOk(isNegativeZero(function () {}), 'function is not negative zero');
+	t.notOk(isNegativeZero(-1), '-1 is not negative zero');
+
+	t.end();
+});
+
+test('negative zero', function (t) {
+	t.ok(isNegativeZero(-0), 'negative zero is negative zero');
+	t.end();
+});
+