- New package app/billing: Init/RecordUsage/Close with auto-migrate - Integration in actionHandler: record tenant_id, operation, msg_count, msg_bytes - Helm chart: billing section in values.yaml, secret-billing.yaml, env vars in deployment - Optional: billing disabled by default (BILLING_PG_HOST not set = no-op) - Table: sqs_usage_records with index on (tenant_id, recorded_at)