fix: pass last_technique_at through row unpacking

backend/routers/creators.py

@@ -82,9 +82,15 @@ async def list_creators(
         creator = row[0]
         tc = row[1] or 0
         vc = row[2] or 0
+        lta = row[3]  # None when creator has 0 techniques
         base = CreatorRead.model_validate(creator)
         items.append(
-            CreatorBrowseItem(**base.model_dump(), technique_count=tc, video_count=vc)
+            CreatorBrowseItem(
+                **base.model_dump(),
+                technique_count=tc,
+                video_count=vc,
+                last_technique_at=lta,
+            )
         )
 
     # Get total count (without offset/limit)