Update the repository to use exception for the delete action.

tui_rsync/core/components/backup_plan/application/repository/backup_plan_repository.py

@@ -1,6 +1,7 @@
 from typing import Optional
 
 from tui_rsync.core.ports.orm import DatabaseManagerPort
+from tui_rsync.core.shared_kernel.ports.Exceptions import CommandException
 from tui_rsync.infrastructure.orm.dto.dtos import BackupPlanDTO
 from .backup_plan_repository_port import BackupPlanRepositoryPort
 
@@ -47,4 +48,8 @@ class BackupPlanRepository(BackupPlanRepositoryPort):
     def delete(self, uuid: UUID) -> bool:
         deleted = BackupPlanModel.delete().where(BackupPlanModel.id == uuid.id).execute()
         deleted = DestinationModel.delete().where(DestinationModel.source == uuid.id).execute() | deleted
-        return bool(deleted)
+
+        if deleted == 0:
+            raise CommandException("Failed to delete the backup plan, because it doesn't exist.")
+
+        return True