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_api_task.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+"""Test creating a task via the scheduler service to simulate API call."""
+
+import asyncio
+from datetime import datetime, timedelta
+
+from app.core.database import get_session_factory
+from app.main import get_global_scheduler_service
+from app.models.scheduled_task import TaskType, RecurrenceType
+
+async def test_api_task_creation():
+    """Test creating a task through the scheduler service (simulates API call)."""
+    try:
+        scheduler_service = get_global_scheduler_service()
+        
+        # Create a task for 2 minutes from now
+        future_time = datetime.utcnow() + timedelta(minutes=2)
+        
+        print(f"Creating task scheduled for: {future_time}")
+        print(f"Current time: {datetime.utcnow()}")
+        
+        task = await scheduler_service.create_task(
+            name=f"API Test Task {future_time.strftime('%H:%M:%S')}",
+            task_type=TaskType.PLAY_SOUND,
+            scheduled_at=future_time,
+            parameters={"sound_id": 1},
+            user_id=1,
+            timezone="UTC",
+            recurrence_type=RecurrenceType.NONE,
+        )
+        
+        print(f"Created task: {task.name} (ID: {task.id})")
+        print(f"Task will execute in: {future_time - datetime.utcnow()}")
+        print("Task should be automatically scheduled in APScheduler!")
+        
+    except Exception as e:
+        print(f"Error: {e}")
+
+if __name__ == "__main__":
+    asyncio.run(test_api_task_creation())