Match Ghostfolio PostgreSQL major version

apps/ghostfolio-postgresql/cluster/cluster.yaml

@@ -1,11 +1,11 @@
 apiVersion: postgresql.cnpg.io/v1
 kind: Cluster
 metadata:
-  name: ghostfolio-cnpg
+  name: ghostfolio-cnpg18
   namespace: ghostfolio
 spec:
   instances: 1
-  imageName: ghcr.io/cloudnative-pg/postgresql:17.11-standard-trixie
+  imageName: ghcr.io/cloudnative-pg/postgresql:18.6-standard-trixie
   bootstrap:
     initdb:
       database: ghostfolio