Pin blumeops-pg to PostgreSQL 18.3

Replace floating :18 tag with pinned :18.3 (upstream out-of-cycle
release fixing 18.2 regressions). Stamps service as reviewed.

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

service-versions.yaml

@@ -124,10 +124,10 @@ services:
 
   - name: blumeops-pg
     type: argocd
-    last-reviewed: null
-    current-version: null
+    last-reviewed: 2026-02-27
+    current-version: "18.3"
     upstream-source: https://github.com/cloudnative-pg/cloudnative-pg/releases
-    notes: CloudNativePG Cluster resource
+    notes: CloudNativePG Cluster resource; pinned to PG minor version
 
   - name: authentik
     type: argocd