fix(helm): bump CNPG postgresVersion to 18 + update runbook probe image (#56)

The Helm chart was still pinning the CNPG cluster to postgres 16
while the docker-compose stack had moved to postgres:18-alpine in
PR #41. Project audit flagged this as a P0 — version drift between
local dev and a Helm-managed cluster means schema and tooling
behaviour differ in production from what we test in dev.

  - deploy/helm/ai-registry/values.yaml: postgresVersion "16" → "18".
    Renders to ghcr.io/cloudnative-pg/postgresql:18 in the CNPG
    Cluster manifest (verified via `helm template`). Comment now
    documents the parity with PR #41 so the next bump understands
    the relationship.
  - docs/runbook.md: the two `pg-probe` snippets that spin up an
    ephemeral pod for psql-into-the-cluster troubleshooting were
    pulling postgres:16-alpine. Bumped to 18-alpine to match.

Verified: `helm lint` passes, `helm template` produces
`imageName: ghcr.io/cloudnative-pg/postgresql:18` for the Cluster
resource.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: Haibread

deploy/helm/ai-registry/values.yaml

@@ -378,7 +378,10 @@ cnpg:
   enabled: false
   instances: 1
   storageSize: 5Gi
-  postgresVersion: "16"
+  # Major version of the CNPG postgres image. Bumped to "18" to match the
+  # docker-compose stack (postgres:18-alpine, see PR #41); CNPG publishes
+  # ghcr.io/cloudnative-pg/postgresql:18 images.
+  postgresVersion: "18"
 
   # Database and owner created by the initdb bootstrap.
   initdb:

docs/runbook.md

@@ -100,7 +100,7 @@ Common root causes:
 kubectl get svc,ep -l cnpg.io/cluster
 
 # Try the DSN from inside a temporary pod
-kubectl run pg-probe --rm -it --image=postgres:16-alpine -- \
+kubectl run pg-probe --rm -it --image=postgres:18-alpine -- \
   psql "$DATABASE_URL" -c 'select 1'
 ```
 
@@ -129,7 +129,7 @@ See §6 for backup / restore.
 ```sh
 kubectl logs deploy/<release>-server | grep -iE 'migration|sql'
 # Check which version the DB is at:
-kubectl run pg-probe --rm -it --image=postgres:16-alpine -- \
+kubectl run pg-probe --rm -it --image=postgres:18-alpine -- \
   psql "$DATABASE_URL" -c 'select version, dirty from schema_migrations'
 ```