Add comprehensive tests for scheduled task repository, scheduler service, and task handlers

- Implemented tests for ScheduledTaskRepository covering task creation, retrieval, filtering, and status updates.
- Developed tests for SchedulerService including task creation, cancellation, user task retrieval, and maintenance jobs.
- Created tests for TaskHandlerRegistry to validate task execution for various types, including credit recharge and sound playback.
- Ensured proper error handling and edge cases in task execution scenarios.
- Added fixtures and mocks to facilitate isolated testing of services and repositories.

app/api/v1/__init__.py

@@ -12,6 +12,7 @@ from app.api.v1 import (
     main,
     player,
     playlists,
+    scheduler,
     socket,
     sounds,
 )
@@ -28,6 +29,7 @@ api_router.include_router(files.router, tags=["files"])
 api_router.include_router(main.router, tags=["main"])
 api_router.include_router(player.router, tags=["player"])
 api_router.include_router(playlists.router, tags=["playlists"])
+api_router.include_router(scheduler.router, tags=["scheduler"])
 api_router.include_router(socket.router, tags=["socket"])
 api_router.include_router(sounds.router, tags=["sounds"])
 api_router.include_router(admin.router)