- Replace %Struct{} with Struct.t() in all @spec annotations
- Replace length(x) > 0 with x != [] in test assertions
- Fix multi-line spec struct references in weather.ex
Store surface observations (ASOS) and upper-air soundings (RAOB) alongside
QSOs for atmospheric propagation correlation. Three new tables: weather_stations,
surface_observations, and soundings with JSONB profiles and pre-computed derived
parameters (refractivity, gradients, duct detection, stability indices).
Includes IEM API client for historical data import and import script seeded
with 95 ASOS + 9 sounding stations from PropCast coverage area.
