fix: recalculate radar track when station position changes

The station position (stationPos) was captured once at ViewModel construction
and never updated when the user clicked on the map or changed the QTH grid.
This caused the radar track line to simply translate instead of being
recalculated from the new position.

Fix:
- Change stationPos and magDeclination from val to var
- Add collectStationPositionChanges() that observes settingsRepo.stationPosition
- On position change: update stationPos, magDeclination, force celestial
  recompute, and recalculate the satellite track

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/RadarViewModel.kt

@@ -65,8 +65,8 @@ class RadarViewModel(
     private val showToast: IShowToast
 ) : ViewModel() {
 
-    private val stationPos = settingsRepo.stationPosition.value
+    private var stationPos = settingsRepo.stationPosition.value
-    private val magDeclination = sensorsRepo.getMagDeclination(stationPos)
+    private var magDeclination = sensorsRepo.getMagDeclination(stationPos)
     private var compassOffset = settingsRepo.otherSettings.value.radarCompassOffset
     private var compassOffsetElev = settingsRepo.otherSettings.value.radarCompassOffsetElev
     private var transponders: List<SatRadio> = emptyList()
@@ -92,6 +92,7 @@ class RadarViewModel(
 
     init {
         collectSettingsChanges()  // also handles initial sensor subscription
+        collectStationPositionChanges()
         collectPassAndStartTickLoop()
         collectRadioTrackingState()
     }
@@ -138,6 +139,23 @@ class RadarViewModel(
         }
     }
 
+    private fun collectStationPositionChanges() {
+        viewModelScope.launch {
+            settingsRepo.stationPosition.collect { newPos ->
+                if (stationPos != newPos) {
+                    stationPos = newPos
+                    magDeclination = sensorsRepo.getMagDeclination(stationPos)
+                    lastCelestialUpdateMs = 0L // force celestial recompute on next tick
+                    val pass = _uiState.value.currentPass ?: return@collect
+                    if (!pass.isDeepSpace) {
+                        val track = satelliteRepo.getTrack(pass.orbitalObject, stationPos, pass.aosTime, pass.losTime)
+                        _uiState.update { it.copy(satTrack = track) }
+                    }
+                }
+            }
+        }
+    }
+
     // --- Pass loading split into focused functions ---
 
     private fun collectPassAndStartTickLoop() {