Update APIM Load Balancer AI documentation

Added note on using Application Gateway for MSFT Foundry APIs and clarified the role of Azure Load Balancer.

Author: brown9804

0_Azure/3_AzureAI/AIFoundry/demos/13_APIM_LoadBalancer_AI.md

@@ -44,6 +44,10 @@ Last updated: 2026-01-22
 > [!NOTE]
 > For **MSFT Foundry APIs**, you can use **Application Gateway** because it’s HTTP/S‑aware, integrates with APIM, and provides advanced routing + [WAF](https://docs.azure.cn/en-us/web-application-firewall/overview) security. Azure Load Balancer is useful for **internal, low‑level traffic distribution**, but not sufficient on its own for developer‑facing Foundry workloads.  
 
+<img width="567" height="383" alt="image" src="https://github.com/user-attachments/assets/bb67fc6c-5407-49b2-8a1f-52963689d37d" />
+
+From [What is Azure Web Application Firewall?](https://docs.azure.cn/en-us/web-application-firewall/overview)
+
 ## Unified Gateway with APIM
 
 `Applications only call APIM endpoints, not individual Foundry instances. This simplifies SDKs and client logic.`