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.

test_task.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+"""Create a test task for scheduler testing."""
+
+import asyncio
+from datetime import datetime
+
+from app.core.database import get_session_factory
+from app.repositories.scheduled_task import ScheduledTaskRepository
+from app.models.scheduled_task import TaskType, RecurrenceType
+
+async def create_test_task():
+    session_factory = get_session_factory()
+    
+    async with session_factory() as session:
+        repo = ScheduledTaskRepository(session)
+        
+        task_data = {
+            "name": "Live Test Task",
+            "task_type": TaskType.PLAY_SOUND,
+            "scheduled_at": datetime(2025, 8, 28, 15, 21, 0),  # 15:21:00 UTC
+            "timezone": "UTC",
+            "parameters": {"sound_id": 1},
+            "user_id": 1,
+            "recurrence_type": RecurrenceType.NONE,
+        }
+        
+        task = await repo.create(task_data)
+        print(f"Created task: {task.name} (ID: {task.id}) scheduled for {task.scheduled_at}")
+
+if __name__ == "__main__":
+    asyncio.run(create_test_task())