fix: delete answers before questions in update_test to avoid FK violation

Bulk DELETE bypasses ORM cascade — must manually delete child rows first.

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

backend/app/api/tests.py

@@ -170,6 +170,11 @@ async def update_test(test_id: int, data: TestCreate, db: AsyncSession = Depends
         test.time_limit = data.time_limit
         test.allow_navigation_back = data.allow_navigation_back
 
+        # Сначала удаляем ответы (FK: answers.question_id → questions.id)
+        q_ids_result = await db.execute(select(Question.id).where(Question.test_id == test_id))
+        q_ids = [row[0] for row in q_ids_result.fetchall()]
+        if q_ids:
+            await db.execute(delete(Answer).where(Answer.question_id.in_(q_ids)))
         await db.execute(delete(Question).where(Question.test_id == test_id))
         await db.flush()