feat: redesign project pricing export — FOB/DDP basis, variant filename, article column

- Add FOB/DDP basis to export options; DDP multiplies all prices ×1.3
- Rename export file from "pricing" to "{FOB|DDP} {variant}" (e.g. "FOB v1")
- Fix server article missing from CSV summary row (PN вендора column)
- Skip per-row breakdown when neither LOT nor BOM is selected
- Remove empty separator rows between configurations
- Redesign export modal: split into Артикул / Цены / Базис поставки sections

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

internal/handlers/export.go

@@ -48,11 +48,13 @@ type ExportRequest struct {
 }
 
 type ProjectExportOptionsRequest struct {
-	IncludeLOT        bool `json:"include_lot"`
-	IncludeBOM        bool `json:"include_bom"`
-	IncludeEstimate   bool `json:"include_estimate"`
-	IncludeStock      bool `json:"include_stock"`
-	IncludeCompetitor bool `json:"include_competitor"`
+	IncludeLOT        bool    `json:"include_lot"`
+	IncludeBOM        bool    `json:"include_bom"`
+	IncludeEstimate   bool    `json:"include_estimate"`
+	IncludeStock      bool    `json:"include_stock"`
+	IncludeCompetitor bool    `json:"include_competitor"`
+	Basis             string  `json:"basis"`       // "fob" or "ddp"
+	SaleMarkup        float64 `json:"sale_markup"` // DDP multiplier; 0 defaults to 1.3
 }
 
 func (h *ExportHandler) ExportCSV(c *gin.Context) {
@@ -252,6 +254,8 @@ func (h *ExportHandler) ExportProjectPricingCSV(c *gin.Context) {
 		IncludeEstimate:   req.IncludeEstimate,
 		IncludeStock:      req.IncludeStock,
 		IncludeCompetitor: req.IncludeCompetitor,
+		Basis:             req.Basis,
+		SaleMarkup:        req.SaleMarkup,
 	}
 
 	data, err := h.exportService.ProjectToPricingExportData(result.Configs, opts)
@@ -260,7 +264,15 @@ func (h *ExportHandler) ExportProjectPricingCSV(c *gin.Context) {
 		return
 	}
 
-	filename := fmt.Sprintf("%s (%s) pricing.csv", time.Now().Format("2006-01-02"), project.Code)
+	basisLabel := "FOB"
+	if strings.EqualFold(strings.TrimSpace(req.Basis), "ddp") {
+		basisLabel = "DDP"
+	}
+	variantLabel := strings.TrimSpace(project.Variant)
+	if variantLabel == "" {
+		variantLabel = "main"
+	}
+	filename := fmt.Sprintf("%s (%s) %s %s.csv", time.Now().Format("2006-01-02"), project.Code, basisLabel, variantLabel)
 	c.Header("Content-Type", "text/csv; charset=utf-8")
 	c.Header("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))