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>

apps/gitlab/manifests/pgbouncer-pooler.yaml

@@ -70,7 +70,7 @@ spec:
   cluster:
     name: pg-gitlab
   
-  instances: 3
+  instances: 1
   
   type: ro  # Read-Only pooler (connects to replicas)
   

apps/gitlab/values.yaml

@@ -140,8 +140,8 @@ minio:
 registry:
   enabled: true
   hpa:
-    minReplicas: 2
-    maxReplicas: 2
+    minReplicas: 1
+    maxReplicas: 1
   resources:
     requests:
       cpu: 25m
@@ -238,8 +238,8 @@ gitlab:
   # GitLab KAS (Kubernetes Agent Server) - enabled for Kubernetes cluster integration
   kas:
     enabled: true
-    minReplicas: 2
-    maxReplicas: 2
+    minReplicas: 1
+    maxReplicas: 1
     resources:
       requests:
         cpu: 25m
@@ -270,8 +270,8 @@ gitlab:
   # Praefect - Gitaly Cluster routing and transaction manager
   praefect:
     enabled: true
-    minReplicas: 2
-    maxReplicas: 2
+    minReplicas: 1
+    maxReplicas: 1
     
     # Note: Praefect PostgreSQL config is in global.praefect.psql
     
@@ -303,8 +303,8 @@ gitlab:
   
   # Sidekiq background jobs
   sidekiq:
-    minReplicas: 2
-    maxReplicas: 2
+    minReplicas: 1
+    maxReplicas: 1
     
     # Note: hostAliases applied via helmfile postsync hook