feat(studio,stacking,animations,collections): M16 ModBison Studio, object stacking, model animations, and poly collections for MVP 2

backend/app/routers/assets.py

@@ -3,7 +3,8 @@
 import json
 import os
 from pathlib import Path
-from typing import Optional
+from datetime import datetime
+from typing import Optional, Union
 
 from fastapi import APIRouter, Depends, HTTPException, UploadFile, File, Query
 from fastapi.responses import FileResponse
@@ -43,8 +44,8 @@ class AssetResponse(BaseModel):
     world_id: Optional[int]
     owner_id: int
     is_public: bool
-    created_at: str
-    updated_at: str
+    created_at: Union[datetime, str]
+    updated_at: Union[datetime, str]
 
     model_config = {"from_attributes": True}