feat: add manual "转人工" (request human) action for conversations

- Backend: RequestHuman service method changes status from AI_SERVING to PENDING
- Backend: POST /api/dashboard/conversation/request-human endpoint
- Frontend: requestHumanConversation API client
- Frontend: "转人工" button in conversation list dropdown and detail dialog

internal/services/conversation_service.go

@@ -374,6 +374,38 @@ func (s *conversationService) TryOffHoursHandoffByAI(conversationID int64, aiAge
 	return handled, err
 }
 
+func (s *conversationService) RequestHuman(conversationID int64, operator *dto.AuthPrincipal) error {
+	if operator == nil {
+		return errorsx.Unauthorized("未登录或登录已过期")
+	}
+	conversation := s.Get(conversationID)
+	if conversation == nil {
+		return errorsx.InvalidParam("会话不存在")
+	}
+	if conversation.Status != enums.IMConversationStatusAIServing {
+		return errorsx.InvalidParam("当前会话状态不允许转人工")
+	}
+	now := time.Now()
+	return sqls.WithTransaction(func(ctx *sqls.TxContext) error {
+		if err := repositories.ConversationRepository.Updates(ctx.Tx, conversationID, map[string]any{
+			"status":         enums.IMConversationStatusPending,
+			"update_user_id": operator.UserID,
+			"update_user_name": operator.Username,
+			"updated_at":     now,
+		}); err != nil {
+			return err
+		}
+		return ConversationEventLogService.CreateEvent(ctx, conversationID,
+			enums.IMEventTypeTransfer, enums.IMSenderTypeSystem, 0,
+			"管理员手动转人工",
+			buildEventPayload(map[string]any{
+				"operator": operator.Username,
+				"fromStatus": enums.IMConversationStatusAIServing,
+				"toStatus":   enums.IMConversationStatusPending,
+			}))
+	})
+}
+
 func (s *conversationService) CloseConversation(conversationID int64, closeReason string, operator *dto.AuthPrincipal) error {
 	if operator == nil {
 		return errorsx.Unauthorized("未登录或登录已过期")