📦 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/constant.js

@@ -0,0 +1,43 @@
+/*:nodoc:*
+ * class ActionStoreConstant
+ *
+ * This action stores the value specified by the const keyword argument.
+ * (Note that the const keyword argument defaults to the rather unhelpful null.)
+ * The 'store_const' action is most commonly used with optional
+ * arguments that specify some sort of flag.
+ *
+ * This class inherited from [[Action]]
+ **/
+'use strict';
+
+var util = require('util');
+
+var Action = require('../../action');
+
+/*:nodoc:*
+ * new ActionStoreConstant(options)
+ * - options (object): options hash see [[Action.new]]
+ *
+ **/
+var ActionStoreConstant = module.exports = function ActionStoreConstant(options) {
+  options = options || {};
+  options.nargs = 0;
+  if (typeof options.constant === 'undefined') {
+    throw new Error('constant option is required for storeAction');
+  }
+  Action.call(this, options);
+};
+util.inherits(ActionStoreConstant, Action);
+
+/*:nodoc:*
+ * ActionStoreConstant#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
+ **/
+ActionStoreConstant.prototype.call = function (parser, namespace) {
+  namespace.set(this.dest, this.constant);
+};

frontend/node_modules/argparse/lib/action/store/false.js

@@ -0,0 +1,27 @@
+/*:nodoc:*
+ * class ActionStoreFalse
+ *
+ * This action store the values False respectively.
+ * This is special cases of 'storeConst'
+ *
+ * This class inherited from [[Action]]
+ **/
+
+'use strict';
+
+var util = require('util');
+
+var ActionStoreConstant = require('./constant');
+
+/*:nodoc:*
+ * new ActionStoreFalse(options)
+ * - options (object): hash of options see [[Action.new]]
+ *
+ **/
+var ActionStoreFalse = module.exports = function ActionStoreFalse(options) {
+  options = options || {};
+  options.constant = false;
+  options.defaultValue = options.defaultValue !== null ? options.defaultValue : true;
+  ActionStoreConstant.call(this, options);
+};
+util.inherits(ActionStoreFalse, ActionStoreConstant);

frontend/node_modules/argparse/lib/action/store/true.js

@@ -0,0 +1,26 @@
+/*:nodoc:*
+ * class ActionStoreTrue
+ *
+ * This action store the values True respectively.
+ * This isspecial cases of 'storeConst'
+ *
+ * This class inherited from [[Action]]
+ **/
+'use strict';
+
+var util = require('util');
+
+var ActionStoreConstant = require('./constant');
+
+/*:nodoc:*
+ * new ActionStoreTrue(options)
+ * - options (object): options hash see [[Action.new]]
+ *
+ **/
+var ActionStoreTrue = module.exports = function ActionStoreTrue(options) {
+  options = options || {};
+  options.constant = true;
+  options.defaultValue = options.defaultValue !== null ? options.defaultValue : false;
+  ActionStoreConstant.call(this, options);
+};
+util.inherits(ActionStoreTrue, ActionStoreConstant);