Ais Tracks

AIS vessel-activity points for the Polygon Builder context overlay. Per Drewry spec: dots of vessel signals over the last 90 days; admin uses density to spot port / anchorage / waiting areas. Defaults to the dataset's most-recent 90 days even when 'now' is past the data end.

Geometry note (post-2026-05-29): ais.ais_positions.geom is in standard WGS84 lon/lat order (rebuilt by migration 0008 from the surviving lon/lat numeric columns). The historical lat/lon-swapped storage and the ST_FlipCoordinates workaround it required are gone.