Integrate Qiniu upload service and update configuration

- Added Qiniu configuration options to .env.example and config.go for file uploads.
- Refactored main.go to include new Qiniu service and upload handler.
- Updated route registration to accommodate the new upload handler.
- Enhanced documentation to include references for Qiniu upload functionality.
- Removed legacy authentication handler and services to streamline the codebase.

docs/common/README.md

@@ -23,3 +23,6 @@
 
 除登录接口外，其他接口都需要携带登录后返回的 `session_key`（见：`docs/common/auth.md`）。
 
+## 上传（七牛直传）
+
+- `docs/common/upload_qiniu.md`