📦 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/WebpackOptionsDefaulter.js

@@ -0,0 +1,26 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const { applyWebpackOptionsDefaults } = require("./config/defaults");
+const { getNormalizedWebpackOptions } = require("./config/normalization");
+
+/** @typedef {import("./config/normalization").WebpackOptions} WebpackOptions */
+/** @typedef {import("./config/normalization").WebpackOptionsNormalized} WebpackOptionsNormalized */
+
+class WebpackOptionsDefaulter {
+	/**
+	 * @param {WebpackOptions} options webpack options
+	 * @returns {WebpackOptionsNormalized} normalized webpack options
+	 */
+	process(options) {
+		const normalizedOptions = getNormalizedWebpackOptions(options);
+		applyWebpackOptionsDefaults(normalizedOptions);
+		return normalizedOptions;
+	}
+}
+
+module.exports = WebpackOptionsDefaulter;