refactor: replace hardcoded user plan strings with CloudPlan enum (#27675)

api/schedule/clean_unused_datasets_task.py

@@ -9,6 +9,7 @@ from sqlalchemy.exc import SQLAlchemyError
 import app
 from configs import dify_config
 from core.rag.index_processor.index_processor_factory import IndexProcessorFactory
+from enums.cloud_plan import CloudPlan
 from extensions.ext_database import db
 from extensions.ext_redis import redis_client
 from models.dataset import Dataset, DatasetAutoDisableLog, DatasetQuery, Document
@@ -35,7 +36,7 @@ def clean_unused_datasets_task():
         },
         {
             "clean_day": datetime.datetime.now() - datetime.timedelta(days=dify_config.PLAN_PRO_CLEAN_DAY_SETTING),
-            "plan_filter": "sandbox",
+            "plan_filter": CloudPlan.SANDBOX,
             "add_logs": False,
         },
     ]