Per-account "last event received" field, so one silent account can be spotted

Meta sometimes stops sending events for a single connected account while every other account on the same webhook keeps flowing. Nothing in the API shows it: account health only reports canPost / canFetchAnalytics, and the webhook's lastFiredAt is per endpoint, not per account.

Example: one of our Instagram accounts received no comment events for about 5.6 days and no DM events for about 10 days (4 to 14 September), with a valid token and an unchanged connection. Support confirmed it was Meta not sending, and that there was no field we could have watched to catch it.

Ask: on each account (for example in account health or GET /v1/accounts), return the time Zernio last received a webhook event for that account, ideally split into messages and comments. Integrators could then alert on one account going quiet instead of finding out from users days later.