Add Alembic for database migrations and initial migration scripts

- Created alembic.ini configuration file for Alembic migrations.
- Added README file for Alembic with a brief description.
- Implemented env.py for Alembic to manage database migrations.
- Created script.py.mako template for migration scripts.
- Added initial migration script to create database tables.
- Created a migration script to add initial plan and playlist data.
- Updated database initialization to run Alembic migrations.
- Enhanced credit service to automatically recharge user credits based on their plan.
- Implemented delete_task method in scheduler service to remove scheduled tasks.
- Updated scheduler API to reflect task deletion instead of cancellation.
- Added CLI tool for managing database migrations.
- Updated tests to cover new functionality for task deletion and credit recharge.
- Updated pyproject.toml and lock files to include Alembic as a dependency.

tests/test_scheduler_service.py

@@ -174,6 +174,39 @@ class TestSchedulerService:
         result = await scheduler_service.cancel_task(uuid.uuid4())
         assert result is False
 
+    async def test_delete_task(
+        self,
+        scheduler_service: SchedulerService,
+        sample_task_data: dict,
+    ):
+        """Test deleting a task."""
+        # Create a task first
+        with patch.object(scheduler_service, "_schedule_apscheduler_job"):
+            schema = self._create_task_schema(sample_task_data)
+            task = await scheduler_service.create_task(task_data=schema)
+
+        # Mock the scheduler remove_job method
+        with patch.object(scheduler_service.scheduler, "remove_job") as mock_remove:
+            result = await scheduler_service.delete_task(task.id)
+
+            assert result is True
+            mock_remove.assert_called_once_with(str(task.id))
+
+            # Check task is completely deleted from database
+            from app.repositories.scheduled_task import ScheduledTaskRepository
+            async with scheduler_service.db_session_factory() as session:
+                repo = ScheduledTaskRepository(session)
+                deleted_task = await repo.get_by_id(task.id)
+                assert deleted_task is None
+
+    async def test_delete_nonexistent_task(
+        self,
+        scheduler_service: SchedulerService,
+    ):
+        """Test deleting a non-existent task."""
+        result = await scheduler_service.delete_task(uuid.uuid4())
+        assert result is False
+
     async def test_get_user_tasks(
         self,
         scheduler_service: SchedulerService,