📦 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/dependencies/AMDRequireDependenciesBlock.js

@@ -0,0 +1,28 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const AsyncDependenciesBlock = require("../AsyncDependenciesBlock");
+const makeSerializable = require("../util/makeSerializable");
+
+/** @typedef {import("../Dependency").DependencyLocation} DependencyLocation */
+
+class AMDRequireDependenciesBlock extends AsyncDependenciesBlock {
+	/**
+	 * @param {DependencyLocation} loc location info
+	 * @param {string=} request request
+	 */
+	constructor(loc, request) {
+		super(null, loc, request);
+	}
+}
+
+makeSerializable(
+	AMDRequireDependenciesBlock,
+	"webpack/lib/dependencies/AMDRequireDependenciesBlock"
+);
+
+module.exports = AMDRequireDependenciesBlock;