More prominent, real-time notifications (with admin controls)

Learners aren't seeing new content or urgent comms until they actively refresh Thrive. We need more prominent, real-time notification options — think pop-ups, sounds, or visual alerts — so admins can reach users instantly without relying on external channels like email or Teams.

Crucially, this should be admin-configurable: some customers want loud, urgent alerts; others would turn them off entirely. A toggle-based notification settings panel would let each customer tailor the experience to how they actually use Thrive.