List conversion events

Returns the most recent conversion events sent through POST /v1/whatsapp/conversions for the given WhatsApp account. Sourced from delivery logs (Axiom late dataset), so the visible window is bounded by log retention (about 30 days). Useful for rendering a "recent activity" panel on the conversions setup tab without standing up a parallel persistence layer.

Per-event payload mirrors the structured log we write on every successful send: eventName, conversationId, eventsReceived, eventsFailed, traceId, durationMs, and the wall-clock timestamp.