better time usings

src/server/models/download.py

@@ -6,7 +6,7 @@ on serialization, validation, and OpenAPI documentation.
 """
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime, timezone
 from enum import Enum
 from typing import List, Optional
 
@@ -80,8 +80,8 @@ class DownloadItem(BaseModel):
     
     # Timestamps
     added_at: datetime = Field(
-        default_factory=datetime.utcnow,
-        description="When item was added to queue"
+        default_factory=lambda: datetime.now(timezone.utc),
+        description="When item was added to queue",
     )
     started_at: Optional[datetime] = Field(
         None, description="When download started"