Add security badge to README for consistency

Author: Raphasha27

README.md

@@ -10,6 +10,8 @@
 
 ## Overview
 
+[![Security](https://img.shields.io/badge/Security-Policy-1f6feb?style=for-the-badge&logo=github)](SECURITY.md)
+
 Intelligent appointment management engine that predicts no-shows using AI and assigns trust scores to clients. Built for service providers who want to reduce revenue loss from missed appointments.
 
 ## How It Works