* settings to configure upload progress notifications (none/standard/detailed)
* use native Android notifications to show progress information
* e.g. 50% (30/60) assets
* e.g. Uploading asset XYZ - 25% (2/8MB)
* no longer show errors if canceled by system (losing network)
* show notifications on background backup errors
* settings page to configure (background backup error) notifications
* persist time since failed background backup
* fix darkmode slider color