Add a server-side REST poller for VesselAPI (free tier 150 calls/mo) that
upserts last-known positions into the shared vessel_last_known store when
AISStream is unset. Default box is the Strait of Hormuz (span 3.6 <= 4 deg),
never CONUS/NC (AISStream owns US coasts).
- app/vesselapi.py: worker loop, 4deg span validator, position->marker
transform (skip suspected_glitch), durable Postgres daily-quota table.
- Local hard cap 5 successful 2xx/UTC day (VESSELAPI_MAX_CALLS_PER_DAY),
monthly floor from X-RateLimit-Remaining, single request limit=50, no
nextToken, no filter.sat, no retry-storm.
- keystore VESSELAPI_API_KEY registry entry; config + compose env passthrough
(app + ingest); wired next to AISStream in main.py lifespan + run_ingester.
- GET /api/vessels docstring notes AISStream and/or VesselAPI cache.
- tests/test_vesselapi.py: 20 unit tests (no network/DB).
