iOS 1.0.1: mini player, Now Playing spacing, play spinner fix

- Mini player floats as a solid card and every screen leaves room for it,
  so it no longer covers the bottom of lists
- More space between title and scrubber; panel switches animate
- Play button no longer spins forever after changing tracks: the engine
  now always reports buffering on load
- Springier button presses and play/pause symbol transitions

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

ios/Stemify/Engine/StemEngine.swift

@@ -298,6 +298,9 @@ final class StemEngine: @unchecked Sendable {
             session = s
             wantPlay = play
             resetOutput(s)
+            // Starts out buffering so the step that begins playback always reports a change,
+            // even when the last track was already playing.
+            setFlags(false, play)
             publish()
         }
     }