AISStream's live US-coast feed crowds vessel_last_known past _MAX_VESSELS
(6000) and the 'evict oldest seen_at' pass reaps the Hormuz VesselAPI rows,
which are only refreshed every VESSELAPI_INTERVAL (~4.8h). Result: the poller
was fetching 50 Hormuz vessels per 2xx but /api/vessels?bbox=Hormuz stayed
empty. Eviction now skips src=vesselapi rows (falls back to evictable-only,
clamped) so the blind-spot box stays resident between polls.