📦 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/@rushstack/eslint-patch/lib-commonjs/exports/eslint-bulk.js

@@ -0,0 +1,7 @@
+"use strict";
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+Object.defineProperty(exports, "__esModule", { value: true });
+// "lib/exports/eslint-bulk" is the entry point for the @rushstack/eslint-bulk command line front end.
+require("../eslint-bulk-suppressions/cli/start");
+//# sourceMappingURL=eslint-bulk.js.map

frontend/node_modules/@rushstack/eslint-patch/lib-commonjs/exports/eslint-bulk.js.map

@@ -0,0 +1 @@
+{"version":3,"file":"eslint-bulk.js","sourceRoot":"","sources":["../../src/exports/eslint-bulk.ts"],"names":[],"mappings":";AAAA,4FAA4F;AAC5F,2DAA2D;;AAE3D,sGAAsG;AAEtG,iDAA+C","sourcesContent":["// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.\n// See LICENSE in the project root for license information.\n\n// \"lib/exports/eslint-bulk\" is the entry point for the @rushstack/eslint-bulk command line front end.\n\nimport '../eslint-bulk-suppressions/cli/start';\n"]}