Store the last entered offset (kHz) per satellite in SharedPreferences
via SettingsRepo, and restore it when the linear transponder calculator
is shown for that satellite.
Follows the project's MVI/clean architecture:
- ISettingsRepo: getSatelliteOffset / setSatelliteOffset
- SettingsRepo: backed by SharedPreferences
- RadarState: calculatorOffsetKHz field
- RadarAction: ChangeCalculatorOffset
- RadarViewModel: loads offset on SelectTransmitter, saves on change
- CalculatorPage/DopplerFrequencyCalculator: receive offset via params
instead of accessing SharedPreferences directly from the UI layer.
