feat: Funcion de sistema tenants

backend/app/services/token_service.py

@@ -6,7 +6,7 @@ Servicio para gesti├│n de refresh tokens persistentes.
 
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy import select, delete
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from typing import Optional
 import uuid
 import structlog
@@ -56,7 +56,7 @@ class TokenService:
             RefreshToken creado
         """
         # Calcular expiraci├│n
-        expires_at = datetime.utcnow() + timedelta(
+        expires_at = datetime.now(timezone.utc) + timedelta(
             days=settings.REFRESH_TOKEN_EXPIRE_DAYS
         )
         
@@ -232,7 +232,7 @@ class TokenService:
             N├║mero de tokens eliminados
         """
         # Eliminar tokens expirados hace más de 7 días
-        cutoff_date = datetime.utcnow() - timedelta(days=7)
+        cutoff_date = datetime.now(timezone.utc) - timedelta(days=7)
         
         query = delete(RefreshToken).where(
             RefreshToken.expires_at < cutoff_date