src/static/custom-markers.json holds user points of interest
({name, lat, lon, optional note}); the dashboard renders them as pin
markers whose popups show which inundation zone the point sits in, its
P.1 trigger level, and the live 24 h exceedance probability (ray-cast
point-in-polygon against the zone geojson; smallest matching zone wins).
Seeded with the owner's four properties.