Clean backend debug logging and standardize error reporting.

This removes verbose trace output in handlers/services and keeps only actionable error-level logs.

internal/service/chat_service.go

@@ -229,7 +229,6 @@ func (s *chatServiceImpl) SendMessage(ctx context.Context, senderID string, conv
 	}
 
 	// 发送消息给接收者
-	log.Printf("[DEBUG SendMessage] 私聊消息 segments 类型: %T, 值: %+v", message.Segments, message.Segments)
 	wsMsg := websocket.CreateWSMessage(websocket.MessageTypeMessage, websocket.ChatMessage{
 		ID:             message.ID,
 		ConversationID: message.ConversationID,
@@ -250,15 +249,11 @@ func (s *chatServiceImpl) SendMessage(ctx context.Context, senderID string, conv
 			// 如果接收者在线，发送实时消息
 			if s.wsManager != nil {
 				isOnline := s.wsManager.IsUserOnline(p.UserID)
-				log.Printf("[DEBUG SendMessage] 接收者 UserID=%s, 在线状态=%v", p.UserID, isOnline)
 				if isOnline {
-					log.Printf("[DEBUG SendMessage] 发送WebSocket消息给 UserID=%s, 消息类型=%s", p.UserID, wsMsg.Type)
 					s.wsManager.SendToUser(p.UserID, wsMsg)
 				}
 			}
 		}
-	} else {
-		log.Printf("[DEBUG SendMessage] 获取参与者失败: %v", err)
 	}
 
 	_ = participant // 避免未使用变量警告