♻️(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/api/viewsets.py

@@ -39,11 +39,11 @@ from core.recording.worker.factories import (
 from core.recording.worker.mediator import (
     WorkerServiceMediator,
 )
-from core.services.livekit_events_service import (
+from core.services.livekit_events import (
     LiveKitEventsService,
     LiveKitWebhookError,
 )
-from core.services.lobby_service import (
+from core.services.lobby import (
     LobbyParticipantNotFound,
     LobbyService,
 )