The demo account could spend real YouTube quota where the human-only guard was
missing (the channel_detail enrichment already had it):
- channels PATCH: an immediate run_recent_backfill when deep_requested is turned on;
- discovery: the channel-detail enrich on the Discover tab;
- feed get_video_detail: the off-catalog videos.list lookup for a video we don't
store (the DB-hit path stays free; demo now gets a 404 for unknown videos).