♻️(backend) avoid repeating 'service' in python modules

These modules are already stored under the 'service' folder, it was redundant.
Renamed these files based on @lunika feedbacks.

src/backend/core/tests/rooms/test_api_rooms_lobby.py

@@ -14,7 +14,7 @@ from rest_framework.test import APIClient
 from ... import utils
 from ...factories import RoomFactory, UserFactory
 from ...models import RoomAccessLevel
-from ...services.lobby_service import (
+from ...services.lobby import (
     LobbyService,
 )
 

src/backend/core/tests/rooms/test_api_rooms_webhook.py

@@ -12,7 +12,7 @@ from unittest import mock
 import pytest
 from livekit import api
 
-from ...services.livekit_events_service import ActionFailedError, LiveKitEventsService
+from ...services.livekit_events import ActionFailedError, LiveKitEventsService
 
 
 @pytest.fixture