[Chore/Refactor] Use centralized naive_utc_now for UTC datetime operations (#24352)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/core/workflow/entities/workflow_execution.py

@@ -6,12 +6,14 @@ implementation details like tenant_id, app_id, etc.
 """
 
 from collections.abc import Mapping
-from datetime import UTC, datetime
+from datetime import datetime
 from enum import StrEnum
 from typing import Any, Optional
 
 from pydantic import BaseModel, Field
 
+from libs.datetime_utils import naive_utc_now
+
 
 class WorkflowType(StrEnum):
     """
@@ -60,7 +62,7 @@ class WorkflowExecution(BaseModel):
         Calculate elapsed time in seconds.
         If workflow is not finished, use current time.
         """
-        end_time = self.finished_at or datetime.now(UTC).replace(tzinfo=None)
+        end_time = self.finished_at or naive_utc_now()
         return (end_time - self.started_at).total_seconds()
 
     @classmethod