Link ARCHITECTURE.md in SECURITY and DEV-QUICK-START guides

DEV-QUICK-START.md

@@ -6,6 +6,8 @@
 - Node.js 20+
 - pnpm 9+ (for frontend work)
 
+> **Tip**: Read [`ARCHITECTURE.md`](ARCHITECTURE.md) to understand the system design before diving in.
+
 ## Hot-Reload Development Mode
 
 Start the development environment with hot-reload:

SECURITY.md

@@ -4,6 +4,9 @@ This document is the canonical security policy for Pulse. It combines our
 ongoing hardening guidance with the operational checklists that previously lived
 in `docs/SECURITY.md`.
 
+For a high-level overview of the system design and data flow, please refer to
+[`ARCHITECTURE.md`](ARCHITECTURE.md).
+
 ---
 
 ## Critical Security Notice for Container Deployments