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)

.gitea/workflows/deploy.yml

@@ -88,8 +88,11 @@ jobs:
           }
 
           ensure_import 'hcloud_server.control_plane[0]' 'k8s-cluster-cp-1'
+          ensure_import 'hcloud_server.control_plane[1]' 'k8s-cluster-cp-2'
+          ensure_import 'hcloud_server.control_plane[2]' 'k8s-cluster-cp-3'
           ensure_import 'hcloud_server.workers[0]' 'k8s-cluster-worker-1'
           ensure_import 'hcloud_server.workers[1]' 'k8s-cluster-worker-2'
+          ensure_import 'hcloud_server.workers[2]' 'k8s-cluster-worker-3'
 
       - name: Terraform Plan
         id: plan