Make operator's PG role management observable

This area is currently a grey zone in a sense that (a) the operator reports very little about roles and (b) roles are not completely managed by the operator (e.g. not deleted).

So we can consider some of the following for debugging/monitoring/user experience purposes:

1. Add a SQL comment on each created role that contains:
   a. message "Created by the Postgres operator"
   b. time of the last Sync event
   c. a source of the role (Teams API, manifest, infra etc.) and, if applicable, the version of the source
2. Log at least a generic explicit message that an Update even was triggered by users' modifications. It is possible to deduce that from the new secret's creation, but that's not immediately evident to the end user new to the k8s/operator. The current messages are too generic:

level=info msg=""UPDATE" event has been queued"
level=info msg="update of the cluster started"

Start by tracing PostgreSQL role creation and the Sync and Update event paths in the operator. Define which observability improvements are in scope—role comments, source metadata, or explicit user-triggered update logs—and verify that the resulting role information and event messages meet the agreed monitoring needs.