feat(android): pinned similar artists tap through to library; note Following view idea

Pinned similar artists (Deezer related) were non-clickable on Android because
Deezer artists carry no Navidrome id. On tap, resolve the name against the
library (exact case-insensitive match) and navigate to that Navidrome artist if
present, else a short "not in your library" toast.

Also: extend the CHANGELOG "Artist following" backlog idea with a dedicated
"Following" view (grid of followed artists) + follow/unfollow toggle.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

android/app/src/main/kotlin/com/novasonic/app/ui/screen/ArtistDetailScreen.kt

@@ -51,6 +51,7 @@ import com.novasonic.app.ui.component.ItunesDownloadSheet
 import com.novasonic.app.ui.component.SongRow
 import com.novasonic.app.ui.theme.*
 import com.novasonic.app.viewmodel.ArtistViewModel
+import kotlinx.coroutines.launch
 
 @Composable
 fun ArtistDetailScreen(
@@ -66,6 +67,7 @@ fun ArtistDetailScreen(
     val vm: ArtistViewModel = viewModel()
     val state by vm.state.collectAsStateWithLifecycle()
     val context = LocalContext.current
+    val scope = rememberCoroutineScope()
 
     BackHandler(enabled = state.partialAlbum != null) { vm.dismissPartialAlbum() }
     BackHandler(enabled = state.subAlbumItem != null && state.partialAlbum == null) { vm.dismissSubAlbum() }
@@ -340,7 +342,17 @@ fun ArtistDetailScreen(
                     items(state.pinnedRelated, key = { it.artistId ?: 0L }) { rel ->
                         Column(
                             horizontalAlignment = Alignment.CenterHorizontally,
-                            modifier = Modifier.width(70.dp),
+                            modifier = Modifier
+                                .width(70.dp)
+                                // Deezer-related has no Navidrome id → resolve by name on tap; navigate
+                                // if the artist is in the library, else say so.
+                                .clickable {
+                                    scope.launch {
+                                        val id = vm.libraryArtistId(rel.artistName)
+                                        if (id != null && onArtistClick != null) onArtistClick(id)
+                                        else Toast.makeText(context, "Nicht in deiner Bibliothek", Toast.LENGTH_SHORT).show()
+                                    }
+                                },
                         ) {
                             AsyncImage(
                                 model = rel.artworkUrl100,

android/app/src/main/kotlin/com/novasonic/app/viewmodel/ArtistViewModel.kt

@@ -354,6 +354,18 @@ class ArtistViewModel(app: Application, savedState: SavedStateHandle) : AndroidV
         }
     }
 
+    /**
+     * Resolve a (Deezer-related) artist name to a Navidrome library artist id, so a pinned artist's
+     * "Similar" chips are tappable when that artist is actually in the library. Exact name match only
+     * (case-insensitive) to avoid navigating to the wrong artist; null if not in the library.
+     */
+    suspend fun libraryArtistId(name: String?): String? {
+        val n = name?.trim()?.lowercase() ?: return null
+        if (n.isEmpty()) return null
+        val res = runCatching { repo.search(n) }.getOrNull() ?: return null
+        return res.artist.firstOrNull { it.name.trim().lowercase() == n }?.id
+    }
+
     fun clearPin() {
         val id = artistId ?: return
         viewModelScope.launch {