[Improvement] Use LocalBroadcastManager to show notifications

You can use `LocalBroadcastManager` to check if can show notification (the alert dialog one) instead keeping Activity instance in Application. Could lead to memory leaks.

Search the Android project for LocalBroadcastManager, the Application-held Activity instance, and the notification alert-dialog code. First trace how the Activity is retained and how notifications are requested; done means notification behavior remains intact without retaining the Activity from Application. No file or test path is named, so identify the relevant entry points before changing anything.

Written by the indexing model from the issue text.