refactor: унифицировать CSV-экспорт, перенести pricing на сервер

- Вынести sortConfigsByLine() — устранить дублирование sort.Slice
  в ProjectToExportData и ProjectToPricingExportData
- Добавить ConfigToPricingExportData() и ExportConfigPricingCSV handler
- Зарегистрировать POST /api/configs/:uuid/export/pricing
- Заменить клиентский DOM-скрапинг exportPricingCSV() на fetch к новому
  endpoint; артикул теперь включается через pricingConfigSummaryRow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/handlers/export.go

@@ -223,6 +223,63 @@ func (h *ExportHandler) ExportProjectCSV(c *gin.Context) {
 	}
 }
 
+func (h *ExportHandler) ExportConfigPricingCSV(c *gin.Context) {
+	uuid := c.Param("uuid")
+
+	var req ProjectExportOptionsRequest
+	if err := c.ShouldBindJSON(&req); err != nil {
+		RespondError(c, http.StatusBadRequest, "invalid request", err)
+		return
+	}
+
+	config, err := h.configService.GetByUUID(uuid, h.dbUsername)
+	if err != nil {
+		RespondError(c, http.StatusNotFound, "resource not found", err)
+		return
+	}
+
+	opts := services.ProjectPricingExportOptions{
+		IncludeLOT:        req.IncludeLOT,
+		IncludeBOM:        req.IncludeBOM,
+		IncludeEstimate:   req.IncludeEstimate,
+		IncludeStock:      req.IncludeStock,
+		IncludeCompetitor: req.IncludeCompetitor,
+		Basis:             req.Basis,
+		SaleMarkup:        req.SaleMarkup,
+	}
+
+	data, err := h.exportService.ConfigToPricingExportData(config, opts)
+	if err != nil {
+		RespondError(c, http.StatusInternalServerError, "internal server error", err)
+		return
+	}
+
+	basisLabel := "FOB"
+	if strings.EqualFold(strings.TrimSpace(req.Basis), "ddp") {
+		basisLabel = "DDP"
+	}
+
+	projectCode := config.Name
+	if config.ProjectUUID != nil && *config.ProjectUUID != "" {
+		if project, err := h.projectService.GetByUUID(*config.ProjectUUID, h.dbUsername); err == nil && project != nil {
+			projectCode = project.Code
+		}
+	}
+
+	filename := fmt.Sprintf("%s (%s) %s %s SPEC.csv",
+		time.Now().Format("2006-01-02"),
+		projectCode,
+		config.Name,
+		basisLabel,
+	)
+	c.Header("Content-Type", "text/csv; charset=utf-8")
+	c.Header("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))
+
+	if err := h.exportService.ToPricingCSV(c.Writer, data, opts); err != nil {
+		c.Error(err)
+	}
+}
+
 func (h *ExportHandler) ExportProjectPricingCSV(c *gin.Context) {
 	projectUUID := c.Param("uuid")