Look up an airport by 3-letter IATA (e.g. SFO) or 4-letter ICAO (e.g. KSFO) code. Query: code (3-5 chars, alphanumeric). Returns { airport: { id, ident, type, name, latitude, longitude, elevationFt, continent, isoCountry, isoRegion, municipality, scheduledService, icaoCode, iataCode, gpsCode, localCode, wikipediaLink } } or 404 NOT_FOUND.