Count accepted and refused pushes per source instance

Per-instance attempts to declared source API routes, split into received (2xx, including cached answers and GET challenges) and refused (all other answers). Includes authentication, scope, body, rate and IP refusals for existing instances. No payload, credentials, client IP or raw idempotency key is stored. Audit events and counters commit together. Requires observability:read on all Corpora; returns only the key's Organization. Uses the Spec 16 rollup windows and retention. By default lists the largest 100 instance/outcome pairs, with a total across every pair. Use connector_id to read both outcomes of one instance; its total then covers that instance only.