fix(roaming): live coords from shared flow, marker by locator pair, versioned apk

Addresses three review findings:

1. Coordinates now come straight from settingsRepo.stationPosition in the screen (collectAsStateWithLifecycle) — the exact same StateFlow the Settings page shows. Previously a separate ViewModel re-derived them, and it could lag behind the Settings page (user: '设置页更新了站位但漫游页死活不更新'). With the shared source the two pages can never disagree. RoamingViewModel removed; state derivation moved to RoamingState.fromPosition().

2. Red marker placement ported faithfully from the QTH定位器 app: it is driven by the 3rd character pair of the 8-char locator (the 'ih' in OL42ih45), mapped to a 0..1 fraction (lon a=west..x=east, lat inverted a=south..x=north), then scaled to the actual center-cell size. The grid now uses the reference proportions (columns 21.4/56.2/21.4, rows 31.5/35.9/31.7) and fills the screen, so the marker lands accurately on any device.

3. Workflow now uploads a versioned APK (look4sat-<version>.apk instead of look4sat.apk).

Also: Settings 'Other' card rows got vertical spacing (Arrangement.spacedBy) so the new roaming toggle is not glued to the night-mode row.

app/src/main/java/com/rtbishop/look4sat/MainScreen.kt

@@ -86,7 +86,6 @@ import com.rtbishop.look4sat.feature.mutual.MutualViewModel
 import com.rtbishop.look4sat.feature.passes.PassesDestination
 import com.rtbishop.look4sat.feature.radar.RadarDestination
 import com.rtbishop.look4sat.feature.roaming.RoamingScreen
-import com.rtbishop.look4sat.feature.roaming.RoamingViewModel
 import com.rtbishop.look4sat.feature.satellites.SatellitesDestination
 import com.rtbishop.look4sat.feature.settings.SettingsDestination
 
@@ -227,11 +226,7 @@ fun MainScreen(navigateToRadar: () -> Unit = {}) {
                             )
                         }
                         entry<Screen.Roaming> {
-                            val roamingViewModel: RoamingViewModel = viewModel(
-                                viewModelStoreOwner = context as ViewModelStoreOwner,
-                                factory = RoamingViewModel.factory(container)
-                            )
-                            RoamingScreen(viewModel = roamingViewModel)
+                            RoamingScreen()
                         }
                         entry<Screen.Settings> {
                             SettingsDestination()