perf(chat): 优化后台客服会话查询与状态

backend/internal/modules/chat/conversation.go

@@ -53,6 +53,19 @@ func (r *Repository) FindConversation(ctx context.Context, principal Principal,
 		if err != nil {
 			return nil, err
 		}
+		var state model.ChatAdminConversationState
+		if err := db.Where("conversation_id = ? AND admin_user_id = ?", conversation.ID, principal.ID).First(&state).Error; err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
+			return nil, err
+		}
+		var unreadCount int64
+		if err := db.Table("chat_messages AS cm").
+			Where("cm.conversation_id = ?", conversation.ID).
+			Where("cm.sender_type <> ?", "system").
+			Where("NOT (cm.sender_type = ? AND cm.sender_id = ?)", "admin", principal.ID).
+			Where("cm.id > ?", state.LastReadMessageID).
+			Count(&unreadCount).Error; err != nil {
+			return nil, err
+		}
 		dto := ConversationDTO{
 			ID:                 conversation.ID,
 			OrderID:            conversation.OrderID,
@@ -62,11 +75,12 @@ func (r *Repository) FindConversation(ctx context.Context, principal Principal,
 			Title:              conversation.Title,
 			Status:             conversation.Status,
 			Role:               "admin", // 管理员角色
+			AdminRemark:        state.Remark,
 			Participants:       participants,
 			LastMessageID:      conversation.LastMessageID,
 			LastMessagePreview: conversation.LastMessagePreview,
 			LastMessageAt:      conversation.LastMessageAt,
-			UnreadCount:        0, // 管理员不计未读
+			UnreadCount:        unreadCount,
 			CreatedAt:          conversation.CreatedAt,
 			UpdatedAt:          conversation.UpdatedAt,
 		}