Implement the calculator service and cron worker that maintain the verification summaries table. Calculator service: - Picks up to 100 dirty buckets (oldest first) - Marks them as calculating - Runs a single grouped COUNT query against ci_job_artifact_states for all buckets - Upserts results back as clean with accurate counts Calculator worker: - Cron worker gated behind geo_job_artifact_verification_summaries feature flag - Loops until all dirty buckets are processed or 3-minute runtime limit is reached - Uses RuntimeLimiter and deduplicate :until_executed to prevent concurrent runs On deploy: nothing changes. Worker exits immediately (FF disabled, no data to process). **Part of:** #512646