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.

.env.example

@@ -16,3 +16,16 @@ JWT_SECRET=your-secret-key-change-in-production
 SHORT_VIDEO_API_KEY=replace-with-real-key
 SHORT_VIDEO_FREE_QUOTA=20
 SHORT_VIDEO_TIMEOUT_SECONDS=5
+
+# 七牛直传配置（Kodo）
+QINIU_ACCESS_KEY=replace-with-access-key
+QINIU_SECRET_KEY=replace-with-secret-key
+QINIU_BUCKET=replace-with-bucket
+# 上传地址：可保持默认（自动调度），也可以配置具体 Region 的 up 域名
+QINIU_UPLOAD_URL=https://upload.qiniup.com
+# CDN 域名（可选）：用于拼接最终访问地址，例如 https://cdn.example.com
+QINIU_CDN_DOMAIN=
+# 上传 key 前缀（可选）
+QINIU_KEY_PREFIX=uploads/
+# token 有效期（秒）
+QINIU_TOKEN_EXPIRE_SECONDS=300