iOS 1.0.8: stem playlists, karaoke softness slider in lyrics

- Playlists tab splits into Plex and Stem. Plex playlists are unchanged and
  now show their custom poster when one is set.
- Stem playlists live on the device; each song keeps its own mix. Add from
  any song or collection menu, or copy a whole Plex playlist.
- Queue items can carry a mix, which wins over the song's saved mix.
- Softness slider under the Vocals picker in lyrics when set to Soft.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ios/Stemify/UI/Screens/NowPlayingScreen.swift

@@ -912,6 +912,15 @@ private struct LyricsPanel: View {
                 .pickerStyle(.segmented)
             }
             .padding(.horizontal, 28).padding(.top, 8)
+            if g.playback.karaokeVocals == .Soft {
+                let db = g.settings.karaokeSoftDb
+                HStack(spacing: 12) {
+                    Text("Softness").font(.subheadline.weight(.semibold)).foregroundStyle(p.label2)
+                    Slider(value: Binding(get: { Double(db) }, set: { g.playback.setKaraokeSoftDb(Int($0.rounded())) }), in: -30...(-3), step: 1)
+                    Text("\(db) dB").font(.caption).monospacedDigit().foregroundStyle(p.label2).frame(width: 46, alignment: .trailing)
+                }
+                .padding(.horizontal, 28).padding(.top, 8)
+            }
             content
         }
         .task(id: track.ratingKey) { await follow() }