Use 'amount_won' for gift card total in admin view

server/vb/admin.py

@@ -193,7 +193,9 @@ def contest_entries(self, obj: Student) -> int | str:
     @admin.display(description="Gift Card Total")
     def gift_card_total(self, obj: Student) -> str | None:
         """Return the total number of gift cards the student has received."""
-        usd = obj.contest_entries.aggregate(total=models.Sum("amount"))["total"] or 0
+        usd = (
+            obj.contest_entries.aggregate(total=models.Sum("amount_won"))["total"] or 0
+        )
         return f"${usd}" if usd > 0 else ""