📦 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/worker/extract-parser-options-plugin.cjs.map

@@ -0,0 +1 @@
+{"version":3,"names":["extractParserOptionsPlugin","parserOverride","code","opts"],"sources":["../../src/worker/extract-parser-options-plugin.cts"],"sourcesContent":["export = function extractParserOptionsPlugin() {\n  return {\n    parserOverride(code: string, opts: any) {\n      return opts;\n    },\n  };\n};\n"],"mappings":";;iBAAS,SAASA,0BAA0BA,CAAA,EAAG;EAC7C,OAAO;IACLC,cAAcA,CAACC,IAAY,EAAEC,IAAS,EAAE;MACtC,OAAOA,IAAI;IACb;EACF,CAAC;AACH,CAAC","ignoreList":[]}