Backs the sidebar issues/counts aggregate on
nightowl_issues (environment, status, type, assigned_to) so it runs
index-only instead of scanning the wide heap — the scan that timed out
(504 / 30s worker kill) on large BYO tenant tables. Built CONCURRENTLY,
self-heals an INVALID leftover on re-run.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>