📦 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/react-dev-utils/getCSSModuleLocalIdent.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const loaderUtils = require('loader-utils');
+const path = require('path');
+
+module.exports = function getLocalIdent(
+  context,
+  localIdentName,
+  localName,
+  options
+) {
+  // Use the filename or folder name, based on some uses the index.js / index.module.(css|scss|sass) project style
+  const fileNameOrFolder = context.resourcePath.match(
+    /index\.module\.(css|scss|sass)$/
+  )
+    ? '[folder]'
+    : '[name]';
+  // Create a hash based on a the file location and class name. Will be unique across a project, and close to globally unique.
+  const hash = loaderUtils.getHashDigest(
+    path.posix.relative(context.rootContext, context.resourcePath) + localName,
+    'md5',
+    'base64',
+    5
+  );
+  // Use loaderUtils to find the file or folder name
+  const className = loaderUtils.interpolateName(
+    context,
+    fileNameOrFolder + '_' + localName + '__' + hash,
+    options
+  );
+  // Remove the .module that appears in every classname when based on the file and replace all "." with "_".
+  return className.replace('.module_', '_').replace(/\./g, '_');
+};