📦 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/enhanced-resolve/lib/JoinRequestPartPlugin.js

@@ -0,0 +1,75 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+/** @typedef {import("./Resolver")} Resolver */
+/** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
+/** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */
+
+const namespaceStartCharCode = "@".charCodeAt(0);
+
+module.exports = class JoinRequestPartPlugin {
+	/**
+	 * @param {string | ResolveStepHook} source source
+	 * @param {string | ResolveStepHook} target target
+	 */
+	constructor(source, target) {
+		this.source = source;
+		this.target = target;
+	}
+
+	/**
+	 * @param {Resolver} resolver the resolver
+	 * @returns {void}
+	 */
+	apply(resolver) {
+		const target = resolver.ensureHook(this.target);
+		resolver
+			.getHook(this.source)
+			.tapAsync(
+				"JoinRequestPartPlugin",
+				(request, resolveContext, callback) => {
+					const req = request.request || "";
+					let i = req.indexOf("/", 3);
+
+					if (i >= 0 && req.charCodeAt(2) === namespaceStartCharCode) {
+						i = req.indexOf("/", i + 1);
+					}
+
+					/** @type {string} */
+					let moduleName;
+					/** @type {string} */
+					let remainingRequest;
+					/** @type {boolean} */
+					let fullySpecified;
+					if (i < 0) {
+						moduleName = req;
+						remainingRequest = ".";
+						fullySpecified = false;
+					} else {
+						moduleName = req.slice(0, i);
+						remainingRequest = `.${req.slice(i)}`;
+						fullySpecified = /** @type {boolean} */ (request.fullySpecified);
+					}
+					/** @type {ResolveRequest} */
+					const obj = {
+						...request,
+						path: resolver.join(
+							/** @type {string} */
+							(request.path),
+							moduleName,
+						),
+						relativePath:
+							request.relativePath &&
+							resolver.join(request.relativePath, moduleName),
+						request: remainingRequest,
+						fullySpecified,
+					};
+					resolver.doResolve(target, obj, null, resolveContext, callback);
+				},
+			);
+	}
+};