Scale down non-critical replicas for homelab resource savings

Reduce replicas to 1 for workloads that don't need HA in a homelab:
- Prometheus 2→1, Alertmanager 2→1 (~4.4GB RAM saved)
- cert-manager 3→1
- GitLab: registry 2→1, kas 2→1, sidekiq 2→1, praefect 2→1,
  pgbouncer-ro 3→1
- Guacamole + guacd 2→1
- Kiali 2→1, ArgoCD server 2→1
- Kyverno background-controller 2→1
- Scylla operator 2→1
- ext-authz-proxy 2→1, netbird-cluster-router 2→1

Kept multi-replica: coredns, envoy-gateway, kyverno admission,
vault, argocd-repo-server, gitlab-webservice, istiod, rook-ceph CSI.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infrastructure/kiali/manifests/kiali-cr.yaml

@@ -9,7 +9,7 @@ spec:
   deployment:
     namespace: istio-system
     cluster_wide_access: true
-    replicas: 2
+    replicas: 1
     pod_labels:
       sidecar.istio.io/inject: "true"
       istio.io/dataplane-mode: "none"