Refactor scheduled task repository and schemas for improved type hints and consistency

- Updated type hints from List/Optional to list/None for better readability and consistency across the codebase.
- Refactored import statements for better organization and clarity.
- Enhanced the ScheduledTaskBase schema to use modern type hints.
- Cleaned up unnecessary comments and whitespace in various files.
- Improved error handling and logging in task execution handlers.
- Updated test cases to reflect changes in type hints and ensure compatibility with the new structure.

tests/test_scheduled_task_repository.py

@@ -2,7 +2,6 @@
 
 import uuid
 from datetime import datetime, timedelta
-from typing import List
 
 import pytest
 from sqlmodel.ext.asyncio.session import AsyncSession
@@ -491,4 +490,4 @@ class TestScheduledTaskRepository:
         updated_task = await repository.get_by_id(sample_task.id)
         assert updated_task.status == TaskStatus.FAILED
         # Non-recurring tasks should be deactivated on failure
-        assert updated_task.is_active is False
+        assert updated_task.is_active is False