fix: openclaw policy violation + reduce memory requests for capacity

- openclaw: fix Kyverno policy violation (node:22-alpine ->
  docker.io/library/node:22-alpine), reduce request to 1536Mi
  with 2Gi limit for overcommit
- rybbit/clickhouse: reduce 1Gi -> 768Mi (frees 256Mi)
- stirling-pdf: reduce 1536Mi -> 1200Mi (frees 336Mi)

stacks/rybbit/main.tf

@@ -302,10 +302,10 @@ resource "kubernetes_deployment" "rybbit" {
           resources {
             requests = {
               cpu    = "25m"
-              memory = "1Gi"
+              memory = "768Mi"
             }
             limits = {
-              memory = "1Gi"
+              memory = "768Mi"
             }
           }
         }