Fix HA cluster join via Load Balancer private IP

Changes:
- Use LB private IP (10.0.1.5) instead of public IP for cluster joins
- Add LB private IP to k3s TLS SANs on primary control plane
- This allows secondary CPs and workers to verify certificates when joining via LB

Fixes x509 certificate validation error when joining via LB public IP.

ansible/site.yml

@@ -24,6 +24,7 @@
     k3s_primary_public_ip: "{{ ansible_host }}"
     k3s_primary_ip: "{{ k3s_private_ip }}"
     k3s_node_ip: "{{ k3s_private_ip }}"
+    kube_api_endpoint: "{{ kube_api_endpoint }}"
 
   roles:
     - k3s-server