External player follow up fixes (#1294)

## Description
Fixes some issues when using an external player:
- Send playback started before launching so the last played date is
updated
- Only use VLC's position if >0 since it returns 0 when playback
completes

### Related issues
Follow up to #1256 

### Testing
Emulator & nvidia shield

## Screenshots
N/A

## AI or LLM usage
None

app/src/main/java/com/github/damontecres/wholphin/services/PlaybackLifecycleObserver.kt

@@ -19,14 +19,6 @@ class PlaybackLifecycleObserver
         private var wasPlaying: Boolean? = null
 
         override fun onStart(owner: LifecycleOwner) {
-            // TODO
-//            val lastDest = navigationManager.backStack.lastOrNull()
-//            if (lastDest is Destination.Playback ||
-//                lastDest is Destination.PlaybackList ||
-//                lastDest is Destination.Slideshow
-//            ) {
-//                navigationManager.goBack()
-//            }
             wasPlaying = null
         }