Updated the normalized observation schema to remove duplicate and/or unnecessary fields

internal/normalizers/openweather/common.go

@@ -53,15 +53,6 @@ func inferIsDay(icon string, dt, sunrise, sunset int64) *bool {
 	return nil
 }
 
-// openWeatherIconURL builds the standard OpenWeather icon URL for the given icon code.
-func openWeatherIconURL(icon string) string {
-	icon = strings.TrimSpace(icon)
-	if icon == "" {
-		return ""
-	}
-	return fmt.Sprintf("https://openweathermap.org/img/wn/%s@2x.png", icon)
-}
-
 // openWeatherStationID returns a stable station identifier for the given response.
 // Prefer the OpenWeather city ID when present; otherwise, fall back to coordinates.
 func openWeatherStationID(parsed owmResponse) string {