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/roles/k3s-server/tasks/main.yml

@@ -15,9 +15,9 @@
   set_fact:
     k3s_install_needed: "{{ (not k3s_service.stat.exists) or ((k3s_service_state.stdout | default('')) != 'active') }}"
 
-- name: Wait for primary API on 6443 (secondary only)
+- name: Wait for API endpoint on 6443 (secondary only)
   wait_for:
-    host: "{{ k3s_primary_ip }}"
+    host: "{{ k3s_join_endpoint | default(k3s_primary_ip) }}"
     port: 6443
     state: started
     timeout: 120
@@ -81,7 +81,7 @@
         K3S_TOKEN: "{{ k3s_token }}"
       command: >-
         /tmp/install-k3s.sh server
-        --server https://{{ k3s_primary_ip }}:6443
+        --server https://{{ k3s_join_endpoint | default(k3s_primary_ip) }}:6443
         --advertise-address={{ k3s_node_ip }}
         --node-ip={{ k3s_node_ip }}
         {% if k3s_disable_embedded_ccm | bool %}--disable-cloud-controller{% endif %}