Add covering indexes for recommendation rank ordering, title staleness scans,
and type+status filtering. Replace N+1 per-row staleness checks in cron jobs
with set-based batch queries. Wrap availability refresh in a transaction for
atomicity. Batch episode stills query and use existence check instead of
loading all rows for count.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
