[ci skip] Fix whiteboard priority class mismatch and OnlyOffice OOMKill

- Add priority_class_name to nextcloud whiteboard deployment to match
  Kyverno-injected tier-3-edge priority class
- Add explicit resource limits (4Gi memory) for OnlyOffice document
  server to prevent OOMKill during font generation

modules/kubernetes/nextcloud/main.tf

@@ -72,6 +72,7 @@ resource "kubernetes_deployment" "whiteboard" {
         }
       }
       spec {
+        priority_class_name = "tier-3-edge"
         container {
           image = "ghcr.io/nextcloud-releases/whiteboard:release"
           name  = "whiteboard"