📦 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/loader-utils/lib/isUrlRequest.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const path = require('path');
+
+function isUrlRequest(url, root) {
+  // An URL is not an request if
+
+  // 1. It's an absolute url and it is not `windows` path like `C:\dir\file`
+  if (/^[a-z][a-z0-9+.-]*:/i.test(url) && !path.win32.isAbsolute(url)) {
+    return false;
+  }
+
+  // 2. It's a protocol-relative
+  if (/^\/\//.test(url)) {
+    return false;
+  }
+
+  // 3. It's some kind of url for a template
+  if (/^[{}[\]#*;,'§$%&(=?`´^°<>]/.test(url)) {
+    return false;
+  }
+
+  // 4. It's also not an request if root isn't set and it's a root-relative url
+  if ((root === undefined || root === false) && /^\//.test(url)) {
+    return false;
+  }
+
+  return true;
+}
+
+module.exports = isUrlRequest;