📦 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/es/promise/all-settled.js

@@ -0,0 +1,16 @@
+'use strict';
+require('../../modules/es.array.iterator');
+require('../../modules/es.object.to-string');
+require('../../modules/es.promise');
+require('../../modules/es.promise.all-settled');
+require('../../modules/es.string.iterator');
+var call = require('../../internals/function-call');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Promise = path.Promise;
+var $allSettled = Promise.allSettled;
+
+module.exports = function allSettled(iterable) {
+  return call($allSettled, isCallable(this) ? this : Promise, iterable);
+};

frontend/node_modules/core-js-pure/es/promise/any.js

@@ -0,0 +1,17 @@
+'use strict';
+require('../../modules/es.aggregate-error');
+require('../../modules/es.array.iterator');
+require('../../modules/es.object.to-string');
+require('../../modules/es.promise');
+require('../../modules/es.promise.any');
+require('../../modules/es.string.iterator');
+var call = require('../../internals/function-call');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Promise = path.Promise;
+var $any = Promise.any;
+
+module.exports = function any(iterable) {
+  return call($any, isCallable(this) ? this : Promise, iterable);
+};

frontend/node_modules/core-js-pure/es/promise/finally.js

@@ -0,0 +1,7 @@
+'use strict';
+require('../../modules/es.object.to-string');
+require('../../modules/es.promise');
+require('../../modules/es.promise.finally');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Promise', 'finally');

frontend/node_modules/core-js-pure/es/promise/index.js

@@ -0,0 +1,14 @@
+'use strict';
+require('../../modules/es.aggregate-error');
+require('../../modules/es.array.iterator');
+require('../../modules/es.object.to-string');
+require('../../modules/es.promise');
+require('../../modules/es.promise.all-settled');
+require('../../modules/es.promise.any');
+require('../../modules/es.promise.try');
+require('../../modules/es.promise.with-resolvers');
+require('../../modules/es.promise.finally');
+require('../../modules/es.string.iterator');
+var path = require('../../internals/path');
+
+module.exports = path.Promise;

frontend/node_modules/core-js-pure/es/promise/try.js

@@ -0,0 +1,15 @@
+'use strict';
+require('../../modules/es.object.to-string');
+require('../../modules/es.promise');
+require('../../modules/es.promise.try');
+var apply = require('../../internals/function-apply');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Promise = path.Promise;
+var $try = Promise['try'];
+
+// eslint-disable-next-line no-unused-vars -- required for arity
+module.exports = { 'try': function (callbackfn /* , ...args */) {
+  return apply($try, isCallable(this) ? this : Promise, arguments);
+} }['try'];

frontend/node_modules/core-js-pure/es/promise/with-resolvers.js

@@ -0,0 +1,13 @@
+'use strict';
+require('../../modules/es.promise');
+require('../../modules/es.promise.with-resolvers');
+var call = require('../../internals/function-call');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Promise = path.Promise;
+var promiseWithResolvers = Promise.withResolvers;
+
+module.exports = function withResolvers() {
+  return call(promiseWithResolvers, isCallable(this) ? this : Promise);
+};