Bundle postgres inside the agentregistry chart by default

[pmuir]

Currently we tell people

Deploy a single-instance PostgreSQL and pgvector into your cluster using the provided example manifest:

kubectl apply -f https://raw.githubusercontent.com/agentregistry-dev/agentregistry/main/examples/postgres-pgvector.yaml
kubectl -n agentregistry wait --for=condition=ready pod -l app=postgres-pgvector --timeout=120s
This setup is intended for development and testing. For production, use a managed PostgreSQL service or a production-grade operator.

Instead, by default, we should include postgres inside the main agentregistry chart, with an option to disable it and configure your own.