fix: revert radar pager to Transceivers tab, default minElev to 0

- Radar pager now defaults to Transceivers tab (initialPage=0)
- Transceivers don't auto-expand (selectedUuid defaults to null)
- Mutual page default minElev changed from settings value to 0.0
- Display filters out portions below the minElev threshold

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

@@ -184,7 +184,7 @@ private fun PagerCard(
     modifier: Modifier = Modifier
 ) {
     val pages = RadarPage.entries
-    val pagerState = rememberPagerState(initialPage = 1, pageCount = { pages.size })
+    val pagerState = rememberPagerState(pageCount = { pages.size })
     val coroutineScope = rememberCoroutineScope()
 
     ElevatedCard(modifier = modifier) {