📦 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/webpack/lib/esm/ExportWebpackRequireRuntimeModule.js

@@ -0,0 +1,30 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+*/
+
+"use strict";
+
+const RuntimeGlobals = require("../RuntimeGlobals");
+const RuntimeModule = require("../RuntimeModule");
+
+class ExportWebpackRequireRuntimeModule extends RuntimeModule {
+	constructor() {
+		super("export webpack runtime", RuntimeModule.STAGE_ATTACH);
+	}
+
+	/**
+	 * @returns {boolean} true, if the runtime module should get it's own scope
+	 */
+	shouldIsolate() {
+		return false;
+	}
+
+	/**
+	 * @returns {string | null} runtime code
+	 */
+	generate() {
+		return `export { ${RuntimeGlobals.require} };`;
+	}
+}
+
+module.exports = ExportWebpackRequireRuntimeModule;