feat(player): persist offline media progress periodically during playback

Add a periodic call to updateWatchProgress in the 5-second progress loop when playing offline media (playbackReportContext == null).

Previously, offline media progress was only written to the Room database on session stop/release. This meant that if playback was interrupted (crash, force-kill) the persisted position would be lost.

Now, the Room offline cache is updated every 5 seconds during offline playback, matching the existing scrobble cadence for online streaming.

core/src/main/java/hu/bbara/purefin/core/player/manager/ProgressManager.kt

@@ -66,11 +66,21 @@ class ProgressManager @Inject constructor(
     private fun startSession(itemId: UUID, positionMs: Long, reportContext: PlaybackReportContext?) {
         activeItemId = itemId
         activePlaybackReportContext = reportContext
+        val isOffline = reportContext == null
         report(itemId, positionMs, reportContext = reportContext, isStart = true)
         progressJob = scope.launch {
             while (isActive) {
                 delay(5000)
                 report(itemId, lastPositionMs, reportContext = activePlaybackReportContext, isPaused = isPaused)
+                if (isOffline) {
+                    scope.launch(Dispatchers.IO) {
+                        try {
+                            mediaMetadataUpdater.updateWatchProgress(itemId, lastPositionMs, lastDurationMs)
+                        } catch (e: Exception) {
+                            Timber.tag(TAG).e(e, "Local cache update failed")
+                        }
+                    }
+                }
             }
         }
     }