Remove unused async database and CRUD modules

- Deleted `database_async.py`, `base_async.py`, and `organization_async.py` modules due to deprecation and unused references across the project.
- Improved overall codebase clarity and minimized redundant functionality by removing unused async database logic, CRUD utilities, and organization-related operations.

backend/app/main.py

@@ -13,7 +13,7 @@ from slowapi.util import get_remote_address
 
 from app.api.main import api_router
 from app.core.config import settings
-from app.core.database_async import check_database_health
+from app.core.database import check_database_health
 from app.core.exceptions import (
     APIException,
     api_exception_handler,