fix(deploy): the ghcr package is private, so declare the pull secret

Same arrangement classic-models already uses: a hand-created ghcr-pull-secret
rather than one committed or held in Vault, since the credential is a GitHub
token that belongs to no estate in particular. Without it the pod would sit in
ImagePullBackOff with no hint as to why.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

k8s/deployment.yaml

@@ -18,6 +18,12 @@ spec:
       labels:
         app: catalogue-agent
     spec:
+      # The ghcr package is private, like classic-models-api's. The secret is
+      # created by hand once (see the README) rather than committed or pulled
+      # from Vault — same arrangement classic-models already uses, and the
+      # credential is a GitHub token that belongs to no estate in particular.
+      imagePullSecrets:
+        - name: ghcr-pull-secret
       securityContext:
         runAsNonRoot: true
         runAsUser: 10001