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/project.yml

@@ -6,8 +6,8 @@ options:
 settings:
   base:
     SWIFT_VERSION: "5.0"
-    MARKETING_VERSION: "1.0.7"
-    CURRENT_PROJECT_VERSION: "8"
+    MARKETING_VERSION: "1.0.8"
+    CURRENT_PROJECT_VERSION: "9"
 targets:
   Stemify:
     type: application