Switch the two deep-scan system automations from a rolling 7-day interval to
weekly_time at 02:00 server-local — TV Mondays, Movies Tuesdays. Different days
means they never overlap, and a fixed wall-clock time doesn't drift with restarts.
Drop initial_delay (the seeder arms timed system triggers). _fix_deep_scan_schedules
migrates the original interval rows to the weekly schedule (the seeder only creates
rows, never updates a drifted trigger); it skips once trigger_type is weekly_time so
a hand-tuned day/time sticks. Idempotent.
cf47032660