fix: restore main runtime sources and cache consistency

exam_pkg/local_db.py

@@ -170,8 +170,9 @@ class ExamLocalDB:
                 VALUES (?, ?, ?, ?, ?, ?, ?, ?)
             ''', (exam_id, name, description, total_score, len(questions), duration, 'published', created_by))
 
-            # 关联题目
-            for order, qid in enumerate(question_ids):
+            # 仅关联实际存在的题目，避免无效 ID 触发外键约束。
+            valid_question_ids = [q['id'] for q in questions]
+            for order, qid in enumerate(valid_question_ids):
                 cursor.execute('''
                     INSERT INTO exam_questions (exam_id, question_id, question_order)
                     VALUES (?, ?, ?)
@@ -183,7 +184,7 @@ class ExamLocalDB:
             'total_score': total_score,
             'total_count': len(questions),
             'duration': duration,
-            'question_ids': question_ids
+            'question_ids': valid_question_ids
         }
 
     def get_exam(self, exam_id: str) -> Optional[Dict]: