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.

pyproject.toml

@@ -15,6 +15,7 @@ dependencies = [
     "pydantic-settings==2.10.1",
     "pyjwt==2.10.1",
     "python-socketio==5.13.0",
+    "pytz==2024.1",
     "python-vlc==3.0.21203",
     "sqlmodel==0.0.24",
     "uvicorn[standard]==0.35.0",