feat: add TrackContextMenuModifier SwiftUI view modifier

Music/Views/TrackContextMenuModifier.swift

@@ -0,0 +1,48 @@
+import SwiftUI
+
+// Attaches a context menu matching the track table's right-click menu.
+// No-ops silently when track or config is nil so callers can pass optionals freely.
+struct TrackContextMenuModifier: ViewModifier {
+    let track: Track?
+    let config: TrackContextMenuConfig?
+
+    func body(content: Content) -> some View {
+        if let track, let config {
+            content.contextMenu {
+                if let lastPlaylistName = config.lastUsedPlaylistName,
+                   let onAddToLastPlaylist = config.onAddToLastPlaylist {
+                    Button("Add to \(lastPlaylistName)") {
+                        onAddToLastPlaylist(track)
+                    }
+                    Divider()
+                }
+
+                if !config.playlists.isEmpty {
+                    Menu("Add to Playlist") {
+                        ForEach(config.playlists) { playlist in
+                            Button(playlist.name) {
+                                config.onAddToPlaylist(track, playlist)
+                            }
+                        }
+                    }
+                }
+
+                if config.selectedPlaylist != nil,
+                   let onRemoveFromPlaylist = config.onRemoveFromPlaylist {
+                    Divider()
+                    Button("Remove from Playlist") {
+                        onRemoveFromPlaylist(track)
+                    }
+                }
+            }
+        } else {
+            content
+        }
+    }
+}
+
+extension View {
+    func trackContextMenu(track: Track?, config: TrackContextMenuConfig?) -> some View {
+        modifier(TrackContextMenuModifier(track: track, config: config))
+    }
+}