Implement HA control plane with Load Balancer (3-3 topology)

Major changes:
- Terraform: Scale to 3 control planes (cx23) + 3 workers (cx33)
- Terraform: Add Hetzner Load Balancer (lb11) for Kubernetes API
- Terraform: Add kube_api_lb_ip output
- Ansible: Add community.network collection to requirements
- Ansible: Update inventory to include LB endpoint
- Ansible: Configure secondary CPs and workers to join via LB
- Ansible: Add k3s_join_endpoint variable for HA joins
- Workflow: Add imports for cp-2, cp-3, and worker-3
- Docs: Update STABLE_BASELINE.md with HA topology and phase gates

Topology:
- 3 control planes (cx23 - 2 vCPU, 8GB RAM each)
- 3 workers (cx33 - 4 vCPU, 16GB RAM each)
- 1 Load Balancer (lb11) routing to all 3 control planes on port 6443
- Workers and secondary CPs join via LB endpoint for HA

Cost impact: +~€26/month (2 extra CPs + 1 extra worker + LB)

terraform/outputs.tf

@@ -63,3 +63,8 @@ output "kubeconfig_command" {
   description = "Command to fetch kubeconfig"
   value       = "ssh root@${hcloud_server.control_plane[0].ipv4_address} 'cat /etc/rancher/k3s/k3s.yaml' > kubeconfig && sed -i 's/127.0.0.1/${hcloud_server.control_plane[0].ipv4_address}/g' kubeconfig"
 }
+
+output "kube_api_lb_ip" {
+  description = "Load Balancer IP for Kubernetes API"
+  value       = hcloud_load_balancer.kube_api.ipv4_address
+}