📦 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/utils.js

@@ -0,0 +1,57 @@
+'use strict';
+
+exports.repeat = function (str, num) {
+  var result = '';
+  for (var i = 0; i < num; i++) { result += str; }
+  return result;
+};
+
+exports.arrayEqual = function (a, b) {
+  if (a.length !== b.length) { return false; }
+  for (var i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) { return false; }
+  }
+  return true;
+};
+
+exports.trimChars = function (str, chars) {
+  var start = 0;
+  var end = str.length - 1;
+  while (chars.indexOf(str.charAt(start)) >= 0) { start++; }
+  while (chars.indexOf(str.charAt(end)) >= 0) { end--; }
+  return str.slice(start, end + 1);
+};
+
+exports.capitalize = function (str) {
+  return str.charAt(0).toUpperCase() + str.slice(1);
+};
+
+exports.arrayUnion = function () {
+  var result = [];
+  for (var i = 0, values = {}; i < arguments.length; i++) {
+    var arr = arguments[i];
+    for (var j = 0; j < arr.length; j++) {
+      if (!values[arr[j]]) {
+        values[arr[j]] = true;
+        result.push(arr[j]);
+      }
+    }
+  }
+  return result;
+};
+
+function has(obj, key) {
+  return Object.prototype.hasOwnProperty.call(obj, key);
+}
+
+exports.has = has;
+
+exports.extend = function (dest, src) {
+  for (var i in src) {
+    if (has(src, i)) { dest[i] = src[i]; }
+  }
+};
+
+exports.trimEnd = function (str) {
+  return str.replace(/\s+$/g, '');
+};