📦 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/CaseSensitiveModulesWarning.js

@@ -0,0 +1,72 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const WebpackError = require("./WebpackError");
+
+/** @typedef {import("./Module")} Module */
+/** @typedef {import("./ModuleGraph")} ModuleGraph */
+
+/**
+ * @param {Module[]} modules the modules to be sorted
+ * @returns {Module[]} sorted version of original modules
+ */
+const sortModules = (modules) =>
+	modules.sort((a, b) => {
+		const aIdent = a.identifier();
+		const bIdent = b.identifier();
+		/* istanbul ignore next */
+		if (aIdent < bIdent) return -1;
+		/* istanbul ignore next */
+		if (aIdent > bIdent) return 1;
+		/* istanbul ignore next */
+		return 0;
+	});
+
+/**
+ * @param {Module[]} modules each module from throw
+ * @param {ModuleGraph} moduleGraph the module graph
+ * @returns {string} each message from provided modules
+ */
+const createModulesListMessage = (modules, moduleGraph) =>
+	modules
+		.map((m) => {
+			let message = `* ${m.identifier()}`;
+			const validReasons = [
+				...moduleGraph.getIncomingConnectionsByOriginModule(m).keys()
+			].filter(Boolean);
+
+			if (validReasons.length > 0) {
+				message += `\n    Used by ${validReasons.length} module(s), i. e.`;
+				message += `\n    ${
+					/** @type {Module[]} */ (validReasons)[0].identifier()
+				}`;
+			}
+			return message;
+		})
+		.join("\n");
+
+class CaseSensitiveModulesWarning extends WebpackError {
+	/**
+	 * Creates an instance of CaseSensitiveModulesWarning.
+	 * @param {Iterable<Module>} modules modules that were detected
+	 * @param {ModuleGraph} moduleGraph the module graph
+	 */
+	constructor(modules, moduleGraph) {
+		const sortedModules = sortModules([...modules]);
+		const modulesList = createModulesListMessage(sortedModules, moduleGraph);
+		super(`There are multiple modules with names that only differ in casing.
+This can lead to unexpected behavior when compiling on a filesystem with other case-semantic.
+Use equal casing. Compare these module identifiers:
+${modulesList}`);
+
+		/** @type {string} */
+		this.name = "CaseSensitiveModulesWarning";
+		this.module = sortedModules[0];
+	}
+}
+
+module.exports = CaseSensitiveModulesWarning;