📦 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/async/dir.js

@@ -0,0 +1,43 @@
+'use strict';
+
+Object.defineProperty(exports, "__esModule", {
+    value: true
+});
+
+var _consoleFunc = require('./internal/consoleFunc.js');
+
+var _consoleFunc2 = _interopRequireDefault(_consoleFunc);
+
+function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
+
+/**
+ * Logs the result of an [`async` function]{@link AsyncFunction} to the
+ * `console` using `console.dir` to display the properties of the resulting object.
+ * Only works in Node.js or in browsers that support `console.dir` and
+ * `console.error` (such as FF and Chrome).
+ * If multiple arguments are returned from the async function,
+ * `console.dir` is called on each argument in order.
+ *
+ * @name dir
+ * @static
+ * @memberOf module:Utils
+ * @method
+ * @category Util
+ * @param {AsyncFunction} function - The function you want to eventually apply
+ * all arguments to.
+ * @param {...*} arguments... - Any number of arguments to apply to the function.
+ * @example
+ *
+ * // in a module
+ * var hello = function(name, callback) {
+ *     setTimeout(function() {
+ *         callback(null, {hello: name});
+ *     }, 1000);
+ * };
+ *
+ * // in the node repl
+ * node> async.dir(hello, 'world');
+ * {hello: 'world'}
+ */
+exports.default = (0, _consoleFunc2.default)('dir');
+module.exports = exports.default;