📦 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/argparse/lib/action/store.js

@@ -0,0 +1,50 @@
+/*:nodoc:*
+ * class ActionStore
+ *
+ * This action just stores the argument’s value. This is the default action.
+ *
+ * This class inherited from [[Action]]
+ *
+ **/
+'use strict';
+
+var util = require('util');
+
+var Action = require('../action');
+
+// Constants
+var c = require('../const');
+
+
+/*:nodoc:*
+ * new ActionStore(options)
+ * - options (object): options hash see [[Action.new]]
+ *
+ **/
+var ActionStore = module.exports = function ActionStore(options) {
+  options = options || {};
+  if (this.nargs <= 0) {
+    throw new Error('nargs for store actions must be > 0; if you ' +
+        'have nothing to store, actions such as store ' +
+        'true or store const may be more appropriate');
+
+  }
+  if (typeof this.constant !== 'undefined' && this.nargs !== c.OPTIONAL) {
+    throw new Error('nargs must be OPTIONAL to supply const');
+  }
+  Action.call(this, options);
+};
+util.inherits(ActionStore, Action);
+
+/*:nodoc:*
+ * ActionStore#call(parser, namespace, values, optionString) -> Void
+ * - parser (ArgumentParser): current parser
+ * - namespace (Namespace): namespace for output data
+ * - values (Array): parsed values
+ * - optionString (Array): input option string(not parsed)
+ *
+ * Call the action. Save result in namespace object
+ **/
+ActionStore.prototype.call = function (parser, namespace, values) {
+  namespace.set(this.dest, values);
+};