Update pricelist repository, service, and tests

internal/repository/pricelist.go

@@ -1,7 +1,9 @@
 package repository
 
 import (
+	"errors"
 	"fmt"
+	"strconv"
 	"strings"
 	"time"
 
@@ -210,14 +212,31 @@ func (r *PricelistRepository) GetItems(pricelistID uint, offset, limit int, sear
 func (r *PricelistRepository) GenerateVersion() (string, error) {
 	today := time.Now().Format("2006-01-02")
 
-	var count int64
-	if err := r.db.Model(&models.Pricelist{}).
-		Where("version LIKE ?", today+"%").
-		Count(&count).Error; err != nil {
-		return "", fmt.Errorf("counting today's pricelists: %w", err)
+	var last models.Pricelist
+	err := r.db.Model(&models.Pricelist{}).
+		Select("version").
+		Where("version LIKE ?", today+"-%").
+		Order("version DESC").
+		Limit(1).
+		Take(&last).Error
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return fmt.Sprintf("%s-001", today), nil
+		}
+		return "", fmt.Errorf("loading latest today's pricelist version: %w", err)
 	}
 
-	return fmt.Sprintf("%s-%03d", today, count+1), nil
+	parts := strings.Split(last.Version, "-")
+	if len(parts) < 4 {
+		return "", fmt.Errorf("invalid pricelist version format: %s", last.Version)
+	}
+
+	n, err := strconv.Atoi(parts[len(parts)-1])
+	if err != nil {
+		return "", fmt.Errorf("parsing pricelist sequence %q: %w", parts[len(parts)-1], err)
+	}
+
+	return fmt.Sprintf("%s-%03d", today, n+1), nil
 }
 
 // CanWrite checks if the current database user has INSERT permission on qt_pricelists