feat(android): partial-album detail gets Play/Shuffle + track 3-dot menu

You can still enjoy an incomplete album: the downloaded-tracks section now has
Abspielen + Zufall buttons (play/shuffle the downloaded songs) and each
downloaded row gets the 3-dot context menu, threaded from both artist screens.

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

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

@@ -156,6 +156,7 @@ fun ArtistDetailScreen(
             onPreview    = vm::togglePreview,
             onDownload   = vm::showDownloadSheet,
             onBack       = vm::dismissPartialAlbum,
+            onShowContextMenu = onShowContextMenu,
         )
         return
     }

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

@@ -115,6 +115,7 @@ fun ExploreScreen(
                     onPreview    = vm::togglePreview,
                     onDownload   = vm::showDownloadSheet,
                     onBack       = vm::dismissPartialAlbum,
+                    onShowContextMenu = onShowContextMenu,
                 )
             }
             albumTracks != null && albumItem != null -> {

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

@@ -5,9 +5,12 @@ import androidx.compose.foundation.layout.*
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.itemsIndexed
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.clickable
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material.icons.filled.Download
+import androidx.compose.material.icons.filled.PlayArrow
+import androidx.compose.material.icons.filled.Shuffle
 import androidx.compose.material3.*
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
@@ -41,6 +44,7 @@ fun PartialAlbumScreen(
     onPreview: (ItunesItem) -> Unit,
     onDownload: (ItunesItem) -> Unit,
     onBack: () -> Unit,
+    onShowContextMenu: ((Song) -> Unit)? = null,
 ) {
     val ia = partialAlbum.itunesAlbum
     val nd = partialAlbum.ndAlbum
@@ -96,6 +100,50 @@ fun PartialAlbumScreen(
             .sortedBy { it.trackNumber ?: 999 }
 
         LazyColumn(Modifier.fillMaxSize()) {
+            // ── Play / Shuffle the downloaded tracks (you can still enjoy the album even when not
+            //    every track is downloaded yet) ─────────────────────────────────────────────────
+            if (downloadedSongs.isNotEmpty()) {
+                item {
+                    Row(
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .padding(start = 16.dp, end = 16.dp, top = 12.dp, bottom = 4.dp),
+                        horizontalArrangement = Arrangement.spacedBy(10.dp),
+                    ) {
+                        Row(
+                            verticalAlignment = Alignment.CenterVertically,
+                            horizontalArrangement = Arrangement.Center,
+                            modifier = Modifier
+                                .weight(1f)
+                                .clip(RoundedCornerShape(10.dp))
+                                .background(NsAccent)
+                                .clickable { onPlay(downloadedSongs, 0) }
+                                .padding(vertical = 11.dp),
+                        ) {
+                            Icon(Icons.Default.PlayArrow, null, tint = NsBackground, modifier = Modifier.size(20.dp))
+                            Spacer(Modifier.width(6.dp))
+                            Text("Abspielen", fontFamily = Outfit, fontWeight = FontWeight.SemiBold,
+                                fontSize = 14.sp, color = NsBackground)
+                        }
+                        Row(
+                            verticalAlignment = Alignment.CenterVertically,
+                            horizontalArrangement = Arrangement.Center,
+                            modifier = Modifier
+                                .weight(1f)
+                                .clip(RoundedCornerShape(10.dp))
+                                .background(NsSurface2)
+                                .clickable { onPlay(downloadedSongs.shuffled(), 0) }
+                                .padding(vertical = 11.dp),
+                        ) {
+                            Icon(Icons.Default.Shuffle, null, tint = NsOnSurface, modifier = Modifier.size(18.dp))
+                            Spacer(Modifier.width(6.dp))
+                            Text("Zufall", fontFamily = Outfit, fontWeight = FontWeight.SemiBold,
+                                fontSize = 14.sp, color = NsOnSurface)
+                        }
+                    }
+                }
+            }
+
             // ── Downloaded tracks ─────────────────────────────────────────────
             if (downloadedSongs.isNotEmpty()) {
                 item {
@@ -113,6 +161,7 @@ fun PartialAlbumScreen(
                         starred      = song.starred != null,
                         onPlay       = { onPlay(downloadedSongs, idx) },
                         onStarToggle = {},
+                        onMore       = onShowContextMenu?.let { cb -> { cb(song) } },
                     )
                 }
             }