📦 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/lodash/_arrayAggregator.js

@@ -0,0 +1,22 @@
+/**
+ * A specialized version of `baseAggregator` for arrays.
+ *
+ * @private
+ * @param {Array} [array] The array to iterate over.
+ * @param {Function} setter The function to set `accumulator` values.
+ * @param {Function} iteratee The iteratee to transform keys.
+ * @param {Object} accumulator The initial aggregated object.
+ * @returns {Function} Returns `accumulator`.
+ */
+function arrayAggregator(array, setter, iteratee, accumulator) {
+  var index = -1,
+      length = array == null ? 0 : array.length;
+
+  while (++index < length) {
+    var value = array[index];
+    setter(accumulator, value, iteratee(value), array);
+  }
+  return accumulator;
+}
+
+module.exports = arrayAggregator;