fix(android): name Library tab indices (detekt MagicNumber)

detekt flagged the `3` and `4` branch labels in the `when (selectedTab)`
block. Promoted all five indices to TAB_ARTISTS … TAB_HIDDEN constants
— same shape detekt would have suggested.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryScreen.kt

@@ -91,19 +91,19 @@ fun LibraryScreen(
     ) { inner ->
         Box(modifier = Modifier.fillMaxSize().padding(inner)) {
             when (selectedTab) {
-                0 -> ArtistsTab(viewModel = viewModel, navController = navController)
-                1 -> AlbumsTab(viewModel = viewModel, navController = navController)
-                2 -> ComingSoonTab(
+                TAB_ARTISTS -> ArtistsTab(viewModel = viewModel, navController = navController)
+                TAB_ALBUMS -> AlbumsTab(viewModel = viewModel, navController = navController)
+                TAB_HISTORY -> ComingSoonTab(
                     title = "History",
                     body = "Recent plays will appear here once /api/me/history " +
                         "wiring lands in Phase 9.",
                 )
-                3 -> ComingSoonTab(
+                TAB_LIKED -> ComingSoonTab(
                     title = "Liked",
                     body = "Liked artists, albums, and tracks will appear here " +
                         "once the like-write path lands in Phase 8.",
                 )
-                4 -> ComingSoonTab(
+                TAB_HIDDEN -> ComingSoonTab(
                     title = "Hidden",
                     body = "Tracks you've flagged as bad rips, wrong tags, or " +
                         "duplicates will appear here in Phase 10.",
@@ -113,6 +113,12 @@ fun LibraryScreen(
     }
 }
 
+private const val TAB_ARTISTS = 0
+private const val TAB_ALBUMS = 1
+private const val TAB_HISTORY = 2
+private const val TAB_LIKED = 3
+private const val TAB_HIDDEN = 4
+
 private val LIBRARY_TABS = listOf("Artists", "Albums", "History", "Liked", "Hidden")
 
 @Composable