fix(playback): persist offline playback position across sessions

[mattsigal]

Pull Request

Summary

Fix offline playback progress not being persisted across sessions. After seeking to a position and exiting playback, re-entering the same item would always restart from 0:00 instead of resuming from the saved position.

Related Issues

Link related issues or tickets separated by commas.

• Closes #
• Fixes [Playback] Offline Videos not Syncing Watch Status - Android Mobile #376
• Related to #

Type of Change

• Bug fix
• New feature
• Refactor
• Performance improvement
• UI/UX update
• Documentation update
• Build/CI change
• Other (describe):

Changes Made

List the key changes included in this PR.

OfflinePlaybackTracker.startTracking() called the async stopTracking() without await. The deferred cleanup set _activeItemId = null after the new session had already assigned its item ID, causing every subsequent periodic save and the final exit save to silently return (because _activeItemId was null). Fixes applied across 5 files:

• offline_playback_tracker.dart - Made startTracking() async and await stopTracking() to prevent the race condition. Also snapshots the manager position before cancelling the stream subscription in stopTracking(), and uses max(managerPos, streamPos) as the best position for saves.
• offline_playback_launcher.dart - Reads the start position fresh from the DB via OfflineRepository.getItem() instead of from the potentially stale DownloadedItem passed by the UI. Awaits PlaybackManager.pendingStop first so any in-flight DB write from the previous exit has committed.
• playback_manager.dart - Exposed pendingStop getter for the in-flight stop future. Added currentPlaybackPosition getter that returns the max of backend position, state position, and last known position. Moved _onOfflineStop callback to fire before backend.stop() so the tracker reads a live position. Set _lastKnownPosition in playOffline() for accurate resume.
• video_player_screen.dart - Used context.canPop() with fallback to Navigator.of(context).pop() in _exitPlayback to handle both GoRouter and Navigator contexts.
• connectivity_service.dart - Trigger offline-to-server progress sync when connectivity is restored and the server is reachable.

Platform

• Android
• iOS
• tvOS
• Web
• macOS
• Windows
• Linux
• All / Shared code

Testing

Describe how this change was tested.

• Tested on emulator / simulator
• Tested on physical device
• Manual testing completed - Built on Android Mobile and tested against Windows Desktop
• Not tested (explain why):

Test Steps

1. Download a show/movie for offline viewing
2. Exit the app and enable airplane mode
3. Reopen the app and start offline playback
4. Seek to ~15 minutes and press back to exit playback
5. Re-enter the same item - it should resume from ~15 minutes
6. Exit the app completely, reopen, verify the position is still saved
7. Disable airplane mode - verify the progress syncs to the server

Screenshots (if applicable)

A tale in 6 images...

1. partially played episode while online
2. airplane mode on, showing playback status retained
3. offline playback, fast forwarded to ~16 minutes in
4. leaving playback, 16 minute timestamp retrained
5. airplane mode off, 16 minute timestamp SYNCED
6. Windows Desktop showing new timestamp!

Checklist

• Code builds successfully
• Code follows project style and conventions
• No unnecessary commented-out code
• No new warnings introduced