fix: scope transactional locks to primary records

backend/apps/tickets/replies.py

@@ -38,7 +38,7 @@ def ensure_customer_reply_task(
     if not normalized:
         return None
     analysis = (
-        TicketSupportAnalysis.objects.select_for_update()
+        TicketSupportAnalysis.objects.select_for_update(of=("self",))
         .select_related("ticket", "run", "created_by")
         .get(id=analysis.id)
     )
@@ -106,7 +106,7 @@ def update_customer_reply(
     """使用乐观版本号修订回复，已批准或已发送版本不可被静默覆盖。"""
 
     task = (
-        CustomerReplyTask.objects.select_for_update()
+        CustomerReplyTask.objects.select_for_update(of=("self",))
         .select_related("ticket", "support_analysis")
         .get(id=task.id)
     )
@@ -162,7 +162,7 @@ def approve_customer_reply_for_channel(
     """批准指定回复版本进入唯一渠道会话，不在此函数直接发送消息。"""
 
     task = (
-        CustomerReplyTask.objects.select_for_update()
+        CustomerReplyTask.objects.select_for_update(of=("self",))
         .select_related("ticket", "support_analysis")
         .get(id=task.id)
     )
@@ -227,7 +227,7 @@ def confirm_customer_reply_sent(
     """仅在人工确认或渠道明确送达后标记回复完成并记录审计。"""
 
     task = (
-        CustomerReplyTask.objects.select_for_update()
+        CustomerReplyTask.objects.select_for_update(of=("self",))
         .select_related("ticket", "support_analysis")
         .get(id=task.id)
     )