📦 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/_stringToPath.js

@@ -0,0 +1,27 @@
+var memoizeCapped = require('./_memoizeCapped');
+
+/** Used to match property names within property paths. */
+var rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g;
+
+/** Used to match backslashes in property paths. */
+var reEscapeChar = /\\(\\)?/g;
+
+/**
+ * Converts `string` to a property path array.
+ *
+ * @private
+ * @param {string} string The string to convert.
+ * @returns {Array} Returns the property path array.
+ */
+var stringToPath = memoizeCapped(function(string) {
+  var result = [];
+  if (string.charCodeAt(0) === 46 /* . */) {
+    result.push('');
+  }
+  string.replace(rePropName, function(match, number, quote, subString) {
+    result.push(quote ? subString.replace(reEscapeChar, '$1') : (number || match));
+  });
+  return result;
+});
+
+module.exports = stringToPath;