Apply one frozen page of grouped Mini WAF blocks exactly once (ADR 0109)

The body is passed to the DB unchanged. A page holds up to 80 items: up to 70 groups (one blocked path, project and minute with its exact count and up to 50 client IPs) and drop counts. Each item is validated and its route ownership checked; accepted groups become one Logs row each in the blocked retention category. A retried page answers its stored outcome and writes nothing; the same page id with other bytes is a conflict.