UserTasks delete handler catches wrong exception type, causing 500 errors

[amaydixit11]

File: api/leaderboard/views.py

Line: 657

Problem:

The delete method on UserTasksManage catches UserTasks.DoesNotExist instead of User.DoesNotExist when trying to look up the user:

# Line 655-660
def delete(self, request, *args, **kwargs):
    try:
        user = User.objects.get(username=request.data["username"])
    except UserTasks.DoesNotExist:  # WRONG: should be User.DoesNotExist
        return Response(
            {"error": "User Not Found"}, status=status.HTTP_404_NOT_FOUND
        )

If the user doesn't exist, a User.DoesNotExist exception is raised but NOT caught, causing an unhandled 500 error. The caught exception type (UserTasks.DoesNotExist) never occurs at this location.

Impact: Deleting tasks for non-existent users crashes the API with a 500 server error instead of returning a proper 404 response.

Fix: Change line 657 to except User.DoesNotExist: