Email delivery tracking now works with Resend webhooks

Fixed webhook handler to correctly process Resend's tag format, restoring delivery and bounce status updates.

Bug Fixes

Resend webhook events were silently failing because the handler expected tags as an array but Resend sends them as an object map. This caused every incoming event to throw, preventing deliveredAt and bouncedAt timestamps from being recorded. The handler now correctly accesses tags as object properties, restoring full email delivery tracking.