- GET /api/stats/alerts — total/firing/resolved counts
- GET /api/stats/alerts/top — most frequent alert names (?limit, default 10)
- GET /api/stats/alerts/by-hour — counts for all 24 hours (zeros filled in)
- GET /api/stats/alerts/by-day — counts for all 7 days with names (zeros filled in)
- All endpoints accept optional ?from/?to (YYYY-MM-DD) to filter by received_at