📦 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/html-webpack-plugin/lib/chunksorter.js

@@ -0,0 +1,45 @@
+// @ts-check
+"use strict";
+
+/** @typedef {import("webpack").Compilation} Compilation */
+
+/**
+ * @type {{[sortmode: string] : (entryPointNames: Array<string>, compilation: Compilation, htmlWebpackPluginOptions: any) => Array<string> }}
+ * This file contains different sort methods for the entry chunks names
+ */
+module.exports = {};
+
+/**
+ * Performs identity mapping (no-sort).
+ * @param  {Array<string>} chunks the chunks to sort
+ * @return {Array<string>} The sorted chunks
+ */
+module.exports.none = (chunks) => chunks;
+
+/**
+ * Sort manually by the chunks
+ * @param {string[]} entryPointNames the chunks to sort
+ * @param {Compilation} compilation the webpack compilation
+ * @param {any} htmlWebpackPluginOptions the plugin options
+ * @return {string[]} The sorted chunks
+ */
+module.exports.manual = (
+  entryPointNames,
+  compilation,
+  htmlWebpackPluginOptions,
+) => {
+  const chunks = htmlWebpackPluginOptions.chunks;
+  if (!Array.isArray(chunks)) {
+    return entryPointNames;
+  }
+  // Remove none existing entries from
+  // htmlWebpackPluginOptions.chunks
+  return chunks.filter((entryPointName) => {
+    return compilation.entrypoints.has(entryPointName);
+  });
+};
+
+/**
+ * Defines the default sorter.
+ */
+module.exports.auto = module.exports.none;