Remove NotificationRepositoryFactory, NotificationServicesFactory, and
NotificationRepositoryInterface — all single-consumer abstractions with
no polymorphism benefit. Simplify container registrar to wire services
directly. Extract shared listener logic (sanitizeTenantIds,
resolveDisplayName, resolveUuid) into NotificationListenerTrait,
eliminating duplication across 4 listeners.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>