fix(application): 修复普通用户接收消息数量统计错误

- 移除了对 user_id == 1 的特殊判断，统一了消息数量统计逻辑
- 优化了代码结构，提高了代码的可读性和维护性

backend/application/sse_views.py

@@ -17,9 +17,6 @@ def event_stream(user_id):
         last_db_change_time = cache.get('last_db_change_time', 0)
         # 只有当数据库发生变化时才检查总数
         if last_db_change_time and last_db_change_time > last_sent_time:
-            if user_id == 1:
-                count = MessageCenterTargetUser.objects.filter(is_read=False).count()
-            else:
             count = MessageCenterTargetUser.objects.filter(users=user_id, is_read=False).count()
             yield f"data: {count}\n\n"
             last_sent_time = time.time()