Operator test-notification button for dormancy delivery

Add an operator button to confirm the dormant-vault notification pipeline works before a real vault triggers it.

On the Vault subjects page, a "Send a test notification to me" button dispatches a sample pdv.dormancy warned event for the operator's own account, with the context flagged source=operator_test. Whatever delivery is configured then fires - PDV Mail emails the operator, and any ECA model reacts - so the operator can verify mail configuration and templates (and, later, their ECA models) without waiting for the cron lifecycle.

It touches no real vault and does not change any warn_count; it only dispatches the event. It is shown whether or not dormancy is enabled, since it is useful purely to test delivery. Available to operators with the vault-subjects access.

Note: because it dispatches the real event (to exercise the whole pipeline including ECA), an enabled audit-trail bridge records one pdv.dormancy.warned row for the operator, flagged source=operator_test.