feat: add PuppetDB read-only database user and pooler

PuppetDB requires a separate read-only database user for its read pool.
Without it, it refuses to use the write user for read queries and all
/pdb/query/v4 calls fail with a 500.

- Add puppetdb_read role via CNPG managed.roles with password sourced
  from a new postgres-read-credentials Vault secret
- Grant CONNECT, USAGE, SELECT and default privileges to puppetdb_read
  via postInitApplicationSQL (must also be run manually on existing cluster)
- Add puppet-postgres-pooler-ro Pooler (type: ro) routing to replicas
- Add puppetdb-read-database-conf ConfigMap with read-database.conf
  mounted into /etc/puppetlabs/puppetdb/conf.d/ in the PuppetDB deployment
- Wire OPENVOXDB_READ_POSTGRES_* env vars from the new secret

💘 Generated with Crush

Assisted-by: Claude Sonnet 4.6 via Crush <crush@charm.land>

apps/base/puppet/kustomization.yaml

@@ -12,6 +12,7 @@ resources:
   - vaultstaticsecret.yaml
   - configmap_puppetboard-config.yaml
   - configmap_puppetdb-config.yaml
+  - configmap_puppetdb-read-database.yaml
   - configmap_puppetserver-compiler-config.yaml
   - configmap_puppetserver-init-config.yaml
   - configmap_puppetserver-init-masters-config.yaml