feat: add health check endpoint for monitoring

README.MD

@@ -188,6 +188,7 @@ curl -X PUT "http://localhost:8080/upload/file.txt?v3=SIGNATURE&expires=TIMESTAM
 - **GET /download/{filename}**: Alternative download endpoint
 
 ### Management Endpoints
+- **GET /health**: Health check endpoint for monitoring
 - **GET /metrics**: Prometheus metrics (if enabled)
 - **Various helper endpoints**: Defined in router setup
 
@@ -238,6 +239,11 @@ curl http://localhost:8080/example.jpg -o downloaded_file.jpg
 curl -I http://localhost:8080/example.jpg
 ```
 
+#### Health Check
+```bash
+curl http://localhost:8080/health
+```
+
 ---
 
 ## Setup