📦 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/@babel/eslint-parser/lib/utils/eslint-version.cjs

@@ -0,0 +1,5 @@
+"use strict";
+
+module.exports = parseInt(require("eslint/package.json").version, 10);
+
+//# sourceMappingURL=eslint-version.cjs.map

frontend/node_modules/@babel/eslint-parser/lib/utils/eslint-version.cjs.map

@@ -0,0 +1 @@
+{"version":3,"names":["parseInt","require","version"],"sources":["../../src/utils/eslint-version.cts"],"sourcesContent":["export = parseInt(require(\"eslint/package.json\").version, 10);\n"],"mappings":";;iBAASA,QAAQ,CAACC,OAAO,CAAC,qBAAqB,CAAC,CAACC,OAAO,EAAE,EAAE,CAAC","ignoreList":[]}