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)

ansible/generate_inventory.py

@@ -32,6 +32,7 @@ def main():
     worker_names = outputs["worker_names"]["value"]
     worker_ips = outputs["worker_ips"]["value"]
     worker_private_ips = outputs["worker_private_ips"]["value"]
+    kube_api_lb_ip = outputs.get("kube_api_lb_ip", {}).get("value", control_plane_ips[0])
 
     control_planes = [
         {
@@ -59,6 +60,7 @@ def main():
         "control_planes": control_planes,
         "workers": workers,
         "private_key_file": outputs["ssh_private_key_path"]["value"],
+        "kube_api_lb_ip": kube_api_lb_ip,
     }
 
     env = Environment(loader=FileSystemLoader("."))