refactor(local_ads_management): integrate PendingDeletionsService for undo functionality

- Replace local delete timer with PendingDeletionsService for managing pending deletions
- Update BLoC to handle deletion events from PendingDeletionsService
- Modify state to include last pending deletion ID and snackbar ad title
- Refactor deletion and undo logic to use the new service
- Update comments and documentation to reflect changes

Author: fulleni