📦 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/on-headers/HISTORY.md

@@ -0,0 +1,26 @@
+1.1.0 / 2025-07-17
+==================
+  * - Fix [CVE-2025-7339](https://www.cve.org/CVERecord?id=CVE-2025-7339) ([GHSA-76c9-3jph-rj3q](https://github.com/expressjs/multer/security/advisories/GHSA-76c9-3jph-rj3q))
+
+
+1.0.2 / 2019-02-21
+==================
+
+  * Fix `res.writeHead` patch missing return value
+
+1.0.1 / 2015-09-29
+==================
+
+  * perf: enable strict mode
+
+1.0.0 / 2014-08-10
+==================
+
+  * Honor `res.statusCode` change in `listener`
+  * Move to `jshttp` organization
+  * Prevent `arguments`-related de-opt
+
+0.0.0 / 2014-05-13
+==================
+
+  * Initial implementation