fix(playback): synchronize UI playback state with engine on session restore (#371)

## Summary
codeberg ate my damn commit in #370

## Changes
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## Testing
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## Checklist
- [ ] No new warnings or clippy lints introduced - if so, explain why
- [ ] Code works on all supported platforms (Linux, macOS, Windows) - tested on available platforms
- [ ] Documentation added/updated where needed
- [ ] If using generative AI assistance, disclosure is provided (co-authored-by tag or PR description) - see [here](CONTRIBUTING.md)

Reviewed-on: https://codeberg.org/hummingbird/hummingbird/pulls/371

Author: allison

src/ui/models.rs

@@ -540,7 +540,12 @@ pub fn build_models(
 
     let position: Entity<u64> = cx.new(|_| 0);
     let duration: Entity<u64> = cx.new(|_| 0);
-    let playback_state: Entity<PlaybackState> = cx.new(|_| PlaybackState::Stopped);
+    let default_playback_state = if initial_track.is_some() {
+        PlaybackState::Paused
+    } else {
+        PlaybackState::Stopped
+    };
+    let playback_state: Entity<PlaybackState> = cx.new(|_| default_playback_state);
     let current_track: Entity<Option<CurrentTrack>> = cx.new(|_| initial_track);
     let shuffling: Entity<bool> = cx.new(|_| initial_shuffle);
     let repeating: Entity<RepeatState> = cx.new(|_| initial_repeat);