📦 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/underscore/modules/restArguments.js

@@ -0,0 +1,27 @@
+// Some functions take a variable number of arguments, or a few expected
+// arguments at the beginning and then a variable number of values to operate
+// on. This helper accumulates all remaining arguments past the function’s
+// argument length (or an explicit `startIndex`), into an array that becomes
+// the last argument. Similar to ES6’s "rest parameter".
+export default function restArguments(func, startIndex) {
+  startIndex = startIndex == null ? func.length - 1 : +startIndex;
+  return function() {
+    var length = Math.max(arguments.length - startIndex, 0),
+        rest = Array(length),
+        index = 0;
+    for (; index < length; index++) {
+      rest[index] = arguments[index + startIndex];
+    }
+    switch (startIndex) {
+      case 0: return func.call(this, rest);
+      case 1: return func.call(this, arguments[0], rest);
+      case 2: return func.call(this, arguments[0], arguments[1], rest);
+    }
+    var args = Array(startIndex + 1);
+    for (index = 0; index < startIndex; index++) {
+      args[index] = arguments[index];
+    }
+    args[startIndex] = rest;
+    return func.apply(this, args);
+  };
+}