Fix article category fallback for pricelist gaps

internal/localdb/components.go

@@ -242,6 +242,31 @@ func (l *LocalDB) GetLocalComponent(lotName string) (*LocalComponent, error) {
 	return &component, nil
 }
 
+// GetLocalComponentCategoriesByLotNames returns category for each lot_name in the local component cache.
+// Missing lots are not included in the map; caller is responsible for strict validation.
+func (l *LocalDB) GetLocalComponentCategoriesByLotNames(lotNames []string) (map[string]string, error) {
+	result := make(map[string]string, len(lotNames))
+	if len(lotNames) == 0 {
+		return result, nil
+	}
+
+	type row struct {
+		LotName  string `gorm:"column:lot_name"`
+		Category string `gorm:"column:category"`
+	}
+	var rows []row
+	if err := l.db.Model(&LocalComponent{}).
+		Select("lot_name, category").
+		Where("lot_name IN ?", lotNames).
+		Find(&rows).Error; err != nil {
+		return nil, err
+	}
+	for _, r := range rows {
+		result[r.LotName] = r.Category
+	}
+	return result, nil
+}
+
 // GetLocalComponentCategories returns distinct categories from local components
 func (l *LocalDB) GetLocalComponentCategories() ([]string, error) {
 	var categories []string
@@ -302,4 +327,3 @@ func (l *LocalDB) NeedComponentSync(maxAgeHours int) bool {
 	}
 	return time.Since(*syncTime).Hours() > float64(maxAgeHours)
 }
-