trpc-query-writing-data-breaks-cron-and-idempotency

Using a tRPC query procedure (GET-equivalent) to both check and write notification records violates the read-only/idempotent query contract and means reminders only fire when a user manually hits the endpoint. Any notification or scheduled-action system must use a mutation procedure triggered by a real cron job, not a query. This is a silent correctness bug — the app appears to support reminders but they never fire in production.