"Delivery event tracking" section on the core Email Sending settings page (/admin/settings/email-sending) — the unified, registry-driven admin panel from the universalization spec (dev_docs/specs/ 2026-07-26-email-event-tracking-universalization-spec.md §5). One row per EventTrackerRegistry.trackers/0 entry; a new provider (Mailgun, …) appears automatically once it registers, no panel code to touch.

Replaces the polling controls that used to live in the two separate provider settings sections (amazon_ses_sqs, brevo_events) — see those modules' moduledocs for what stayed behind (transport/identity config, not polling).

"Poll now" vs poll_cycle/1

EventTracker.poll_cycle/1's own moduledoc anticipated this button calling it directly (a synchronous, in-process cycle). This panel calls each tracker's poll_now/0 instead (see EventTrackerRegistry's duck-typed "Manager API"): it already exists, already handles the "force a poll even while the toggle is off" case explicitly, and enqueues via Oban rather than blocking the LiveView process for a network round trip. poll_cycle/1 stays defined (still satisfies the behaviour) but unused here — a deliberate choice, not an oversight.