Fix n8n, gitlab, and netbird-operator degraded states

- n8n: Set replicaCount=1 (RWO PVC incompatible with multiple replicas),
  add resource limits to satisfy Kyverno policy
- gitlab: Add ignoreDifferences for redis-gitlab-additional service
  (port names and selectors managed by Redis operator)
- netbird-operator: Add ExternalSecret for netbird-mgmt-api-key in
  netbird namespace and add manifests source to Application

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

argocd-apps/apps/gitlab.yaml

@@ -25,6 +25,14 @@ spec:
   destination:
     server: https://kubernetes.default.svc
     namespace: gitlab
+  ignoreDifferences:
+    # Redis operator reconciles this service with different port names and selectors
+    - group: ""
+      kind: Service
+      name: redis-gitlab-additional
+      jsonPointers:
+        - /spec/ports
+        - /spec/selector
   syncPolicy:
     automated:
       prune: true