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.

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsScreen.kt

@@ -490,7 +490,10 @@ private fun OtherCard(settings: OtherSettings, onAction: (SettingsAction) -> Uni
             .fillMaxWidth()
             .height(296.dp)
     ) {
-        Column(modifier = Modifier.padding(horizontal = 8.dp, vertical = 4.dp)) {
+        Column(
+            modifier = Modifier.padding(horizontal = 8.dp, vertical = 4.dp),
+            verticalArrangement = Arrangement.spacedBy(4.dp)
+        ) {
             Text(
                 text = stringResource(id = R.string.prefs_other_title),
                 color = MaterialTheme.colorScheme.primary