📦 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/core-js-pure/internals/promise-resolve.js

@@ -0,0 +1,13 @@
+'use strict';
+var anObject = require('../internals/an-object');
+var isObject = require('../internals/is-object');
+var newPromiseCapability = require('../internals/new-promise-capability');
+
+module.exports = function (C, x) {
+  anObject(C);
+  if (isObject(x) && x.constructor === C) return x;
+  var promiseCapability = newPromiseCapability.f(C);
+  var resolve = promiseCapability.resolve;
+  resolve(x);
+  return promiseCapability.promise;
+};