📦 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/eslint/lib/cli-engine/hash.js

@@ -0,0 +1,35 @@
+/**
+ * @fileoverview Defining the hashing function in one place.
+ * @author Michael Ficarra
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const murmur = require("imurmurhash");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+//------------------------------------------------------------------------------
+// Private
+//------------------------------------------------------------------------------
+
+/**
+ * hash the given string
+ * @param {string} str the string to hash
+ * @returns {string} the hash
+ */
+function hash(str) {
+    return murmur(str).result().toString(36);
+}
+
+//------------------------------------------------------------------------------
+// Public Interface
+//------------------------------------------------------------------------------
+
+module.exports = hash;