Refactor code structure for improved readability and maintainability

docs/architecture/README.md

@@ -5,6 +5,7 @@
 ## Table of Contents
 
 - [Introduction and Goals](#introduction-and-goals)
+- [Companion Documentation](#companion-documentation)
 - [Architecture Constraints](#architecture-constraints)
 - [Context and Scope](#context-and-scope)
 - [Solution Strategy](#solution-strategy)
@@ -17,6 +18,13 @@
 - [Risks and Technical Debts](#risks-and-technical-debts)
 - [Glossary](#glossary)
 
+## Companion Documentation
+
+- [API.md](../../API.md) - Implemented WebSocket and REST API reference.
+- [DEPLOYMENT.md](../../DEPLOYMENT.md) - Production deployment and operational runbook.
+- [MONITORING.md](../../MONITORING.md) - Metrics, dashboards, and monitoring troubleshooting.
+- [SECURITY.md](../../SECURITY.md) - Security model, controls, and hardening baseline.
+
 ## Introduction and Goals
 
 ### Requirements Overview