Next high/low tide predictions near a coordinate. Query: lat (-90..90), lon (-180..180), radius_km (1-500, default 100), hours (1-72, default 24). Returns { query, station:{ id, name, latitude, longitude, state, distanceKm }, predictions[{ time (station local), type: "high"|"low", heightMeters }], source }. Returns 404 NO_STATION if no NOAA tide station is within radius. Heights are referenced to MLLW (Mean Lower-Low Water).