C2(migrate-immich-to-ringtail): impl promote ringtail immich-pg from replica to primary

Row counts verified equal between source (minikube) and replica
(ringtail) across asset (12681), user (1), album (28),
smart_search (9624), activity (0), asset_face (3917). Source immich
is scaled to 0 — no writes since the basebackup completed.

Flipping replica.enabled=false to promote. The externalClusters and
bootstrap.pg_basebackup blocks are left in place as documentation
(CNPG ignores them after initialization).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

argocd/manifests/databases-ringtail/immich-pg.yaml

@@ -21,9 +21,13 @@ spec:
     size: 10Gi
     storageClass: local-path
 
-  # Streaming replica of the minikube source until promoted.
+  # Promoted away from the minikube source on 2026-05-13.
+  # The externalClusters + bootstrap.pg_basebackup blocks below are
+  # ignored by CNPG once the cluster is initialized; left in place
+  # so the manifest documents how this cluster came to exist. Remove
+  # in a follow-up once the minikube source is decommissioned.
   replica:
-    enabled: true
+    enabled: false
     source: source-immich-pg
 
   # Bootstrap from the source via pg_basebackup.