Document AKS internal CIDR ranges to avoid on Mendix on Azure

[MXClyde]

Summary

• Document the AKS internal CIDR ranges (10.0.0.0/16 service CIDR, 10.244.0.0/16 pod CIDR) that every Mendix on Azure cluster reserves internally, so customers don't pick a VNet/on-prem range that overlaps them when planning peering or on-prem connectivity.
• Updates the AKS Node CIDR IP Range portal setting description (also used as the in-portal tooltip) and adds a warning callout with the full peering/on-prem guidance and the Private Endpoints workaround for unavoidable overlap.

Resolves MXFORAZURE-549.

Test plan

• Table renders correctly and the new alert box follows existing Hugo shortcode conventions on this page
• Links/formatting check in docs preview

[MXClyde]

@katarzyna-koltun-mx This is a small, self-contained doc addition (1 file, +12/-1) - can be merged immediately.