Add initial backend implementation

- Go module with Gin, GORM, JWT, excelize dependencies
- Configuration loading from YAML with all settings
- GORM models for users, categories, components, configurations, alerts
- Repository layer for all entities
- Services: auth (JWT), pricing (median/average/weighted), components,
  quotes, configurations, export (CSV/XLSX), alerts
- Middleware: JWT auth, role-based access, CORS
- HTTP handlers for all API endpoints
- Main server with dependency injection and graceful shutdown

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/services/export.go

@@ -0,0 +1,175 @@
+package services
+
+import (
+	"bytes"
+	"encoding/csv"
+	"fmt"
+	"time"
+
+	"github.com/mchus/quoteforge/internal/config"
+	"github.com/mchus/quoteforge/internal/models"
+	"github.com/xuri/excelize/v2"
+)
+
+type ExportService struct {
+	config config.ExportConfig
+}
+
+func NewExportService(cfg config.ExportConfig) *ExportService {
+	return &ExportService{config: cfg}
+}
+
+type ExportData struct {
+	Name       string
+	Items      []ExportItem
+	Total      float64
+	Notes      string
+	CreatedAt  time.Time
+}
+
+type ExportItem struct {
+	LotName     string
+	Description string
+	Category    string
+	Quantity    int
+	UnitPrice   float64
+	TotalPrice  float64
+}
+
+func (s *ExportService) ToCSV(data *ExportData) ([]byte, error) {
+	var buf bytes.Buffer
+	w := csv.NewWriter(&buf)
+
+	// Header
+	headers := []string{"Артикул", "Описание", "Категория", "Количество", "Цена за единицу", "Сумма"}
+	if err := w.Write(headers); err != nil {
+		return nil, err
+	}
+
+	// Items
+	for _, item := range data.Items {
+		row := []string{
+			item.LotName,
+			item.Description,
+			item.Category,
+			fmt.Sprintf("%d", item.Quantity),
+			fmt.Sprintf("%.2f", item.UnitPrice),
+			fmt.Sprintf("%.2f", item.TotalPrice),
+		}
+		if err := w.Write(row); err != nil {
+			return nil, err
+		}
+	}
+
+	// Total row
+	if err := w.Write([]string{"", "", "", "", "ИТОГО:", fmt.Sprintf("%.2f", data.Total)}); err != nil {
+		return nil, err
+	}
+
+	w.Flush()
+	return buf.Bytes(), w.Error()
+}
+
+func (s *ExportService) ToXLSX(data *ExportData) ([]byte, error) {
+	f := excelize.NewFile()
+	sheet := "Конфигурация"
+	f.SetSheetName("Sheet1", sheet)
+
+	// Styles
+	headerStyle, _ := f.NewStyle(&excelize.Style{
+		Font:      &excelize.Font{Bold: true, Size: 12, Color: "#FFFFFF"},
+		Fill:      excelize.Fill{Type: "pattern", Color: []string{"#4472C4"}, Pattern: 1},
+		Alignment: &excelize.Alignment{Horizontal: "center", Vertical: "center"},
+		Border: []excelize.Border{
+			{Type: "left", Color: "#000000", Style: 1},
+			{Type: "top", Color: "#000000", Style: 1},
+			{Type: "bottom", Color: "#000000", Style: 1},
+			{Type: "right", Color: "#000000", Style: 1},
+		},
+	})
+
+	totalStyle, _ := f.NewStyle(&excelize.Style{
+		Font: &excelize.Font{Bold: true, Size: 12},
+		Fill: excelize.Fill{Type: "pattern", Color: []string{"#E2EFDA"}, Pattern: 1},
+	})
+
+	priceStyle, _ := f.NewStyle(&excelize.Style{
+		NumFmt: 4, // #,##0.00
+	})
+
+	// Title
+	f.SetCellValue(sheet, "A1", s.config.CompanyName)
+	f.SetCellValue(sheet, "A2", "Коммерческое предложение: "+data.Name)
+	f.SetCellValue(sheet, "A3", "Дата: "+data.CreatedAt.Format("02.01.2006"))
+
+	// Headers
+	headers := []string{"Артикул", "Описание", "Категория", "Кол-во", "Цена", "Сумма"}
+	for i, h := range headers {
+		cell := fmt.Sprintf("%c5", 'A'+i)
+		f.SetCellValue(sheet, cell, h)
+		f.SetCellStyle(sheet, cell, cell, headerStyle)
+	}
+
+	// Data rows
+	row := 6
+	for _, item := range data.Items {
+		f.SetCellValue(sheet, fmt.Sprintf("A%d", row), item.LotName)
+		f.SetCellValue(sheet, fmt.Sprintf("B%d", row), item.Description)
+		f.SetCellValue(sheet, fmt.Sprintf("C%d", row), item.Category)
+		f.SetCellValue(sheet, fmt.Sprintf("D%d", row), item.Quantity)
+		f.SetCellValue(sheet, fmt.Sprintf("E%d", row), item.UnitPrice)
+		f.SetCellValue(sheet, fmt.Sprintf("F%d", row), item.TotalPrice)
+		f.SetCellStyle(sheet, fmt.Sprintf("E%d", row), fmt.Sprintf("F%d", row), priceStyle)
+		row++
+	}
+
+	// Total row
+	f.SetCellValue(sheet, fmt.Sprintf("E%d", row), "ИТОГО:")
+	f.SetCellValue(sheet, fmt.Sprintf("F%d", row), data.Total)
+	f.SetCellStyle(sheet, fmt.Sprintf("E%d", row), fmt.Sprintf("F%d", row), totalStyle)
+
+	// Notes
+	if data.Notes != "" {
+		row += 2
+		f.SetCellValue(sheet, fmt.Sprintf("A%d", row), "Примечания: "+data.Notes)
+	}
+
+	// Column widths
+	f.SetColWidth(sheet, "A", "A", 25)
+	f.SetColWidth(sheet, "B", "B", 50)
+	f.SetColWidth(sheet, "C", "C", 15)
+	f.SetColWidth(sheet, "D", "D", 10)
+	f.SetColWidth(sheet, "E", "E", 15)
+	f.SetColWidth(sheet, "F", "F", 15)
+
+	var buf bytes.Buffer
+	if err := f.Write(&buf); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (s *ExportService) ConfigToExportData(config *models.Configuration) *ExportData {
+	items := make([]ExportItem, len(config.Items))
+	var total float64
+
+	for i, item := range config.Items {
+		itemTotal := item.UnitPrice * float64(item.Quantity)
+		items[i] = ExportItem{
+			LotName:    item.LotName,
+			Quantity:   item.Quantity,
+			UnitPrice:  item.UnitPrice,
+			TotalPrice: itemTotal,
+		}
+		total += itemTotal
+	}
+
+	return &ExportData{
+		Name:      config.Name,
+		Items:     items,
+		Total:     total,
+		Notes:     config.Notes,
+		CreatedAt: config.CreatedAt,
+	}
+}