Fix QuizAttempt field name: createdAt -> completedAt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/admin/quizzes/[quizId]/page.tsx

@@ -14,7 +14,7 @@ export default async function AdminQuizAttemptsPage({ params }: Props) {
     include: {
       questions: { orderBy: { order: "asc" } },
       attempts: {
-        orderBy: { createdAt: "desc" },
+        orderBy: { completedAt: "desc" },
         include: {
           user: { select: { name: true, email: true } },
         },
@@ -67,7 +67,7 @@ export default async function AdminQuizAttemptsPage({ params }: Props) {
         <div className="space-y-4">
           {quiz.attempts.map((attempt) => {
             const answers = attempt.answers as Record<string, string>;
-            const date = new Date(attempt.createdAt).toLocaleString("ru-RU", {
+            const date = new Date(attempt.completedAt).toLocaleString("ru-RU", {
               day: "2-digit",
               month: "2-digit",
               year: "numeric",