📦 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/ExtensionAliasPlugin.js

@@ -0,0 +1,100 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Ivan Kopeykin @vankop
+*/
+
+"use strict";
+
+const forEachBail = require("./forEachBail");
+
+/** @typedef {import("./Resolver")} Resolver */
+/** @typedef {import("./Resolver").ResolveRequest} ResolveRequest */
+/** @typedef {import("./Resolver").ResolveStepHook} ResolveStepHook */
+/** @typedef {{ alias: string | string[], extension: string }} ExtensionAliasOption */
+
+module.exports = class ExtensionAliasPlugin {
+	/**
+	 * @param {string | ResolveStepHook} source source
+	 * @param {ExtensionAliasOption} options options
+	 * @param {string | ResolveStepHook} target target
+	 */
+	constructor(source, options, target) {
+		this.source = source;
+		this.options = options;
+		this.target = target;
+	}
+
+	/**
+	 * @param {Resolver} resolver the resolver
+	 * @returns {void}
+	 */
+	apply(resolver) {
+		const target = resolver.ensureHook(this.target);
+		const { extension, alias } = this.options;
+		resolver
+			.getHook(this.source)
+			.tapAsync("ExtensionAliasPlugin", (request, resolveContext, callback) => {
+				const requestPath = request.request;
+				if (!requestPath || !requestPath.endsWith(extension)) return callback();
+				const isAliasString = typeof alias === "string";
+				/**
+				 * @param {string} alias extension alias
+				 * @param {(err?: null | Error, result?: null | ResolveRequest) => void} callback callback
+				 * @param {number=} index index
+				 * @returns {void}
+				 */
+				const resolve = (alias, callback, index) => {
+					const newRequest = `${requestPath.slice(
+						0,
+						-extension.length,
+					)}${alias}`;
+
+					return resolver.doResolve(
+						target,
+						{
+							...request,
+							request: newRequest,
+							fullySpecified: true,
+						},
+						`aliased from extension alias with mapping '${extension}' to '${alias}'`,
+						resolveContext,
+						(err, result) => {
+							// Throw error if we are on the last alias (for multiple aliases) and it failed, always throw if we are not an array or we have only one alias
+							if (!isAliasString && index) {
+								if (index !== this.options.alias.length) {
+									if (resolveContext.log) {
+										resolveContext.log(
+											`Failed to alias from extension alias with mapping '${extension}' to '${alias}' for '${newRequest}': ${err}`,
+										);
+									}
+
+									return callback(null, result);
+								}
+
+								return callback(err, result);
+							}
+							callback(err, result);
+						},
+					);
+				};
+				/**
+				 * @param {(null | Error)=} err error
+				 * @param {(null | ResolveRequest)=} result result
+				 * @returns {void}
+				 */
+				const stoppingCallback = (err, result) => {
+					if (err) return callback(err);
+					if (result) return callback(null, result);
+					// Don't allow other aliasing or raw request
+					return callback(null, null);
+				};
+				if (isAliasString) {
+					resolve(alias, stoppingCallback);
+				} else if (alias.length > 1) {
+					forEachBail(alias, resolve, stoppingCallback);
+				} else {
+					resolve(alias[0], stoppingCallback);
+				}
+			});
+	}
+};