init: 后端框架脚手架 (Go + Gin + GORM + MySQL)

- 项目目录结构：backend/ deploy/ schema/ migrations/
- 数据库 Schema：所有建表 SQL，含 hotel_id 多租户隔离
- Go 后端：config、model、handler、service、middleware、router
- 认证：账号密码登录 + JWT（Access + Refresh Token）
- 许可证：HMAC-SHA256 激活码生成 + 设备绑定验证
- 业务模块：商品、仓库、往来单位、入库、出库、库存、盘点
- 库存事务：入库/出库审核时原子更新库存 + 流水记录
- 数据导入：Excel/CSV 批量导入商品、往来单位
- Docker Compose：本地 MySQL + Adminer

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

backend/internal/service/license.go

@@ -0,0 +1,90 @@
+package service
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base32"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"gorm.io/gorm"
+
+	"github.com/wangjia/jiu/backend/config"
+	"github.com/wangjia/jiu/backend/internal/model"
+)
+
+var (
+	ErrLicenseNotFound  = errors.New("license not found")
+	ErrLicenseInactive  = errors.New("license is inactive")
+	ErrLicenseExpired   = errors.New("license has expired")
+	ErrDeviceMismatch   = errors.New("license is bound to another device")
+)
+
+type LicenseService struct {
+	db *gorm.DB
+}
+
+func NewLicenseService(db *gorm.DB) *LicenseService {
+	return &LicenseService{db: db}
+}
+
+// GenerateKey 生成许可证激活码
+// 格式：HMAC-SHA256(hotelID+deviceID+expiry, secret) → base32, 每5字符加'-'
+func GenerateKey(hotelID uint64, licenseType string, expiresAt *time.Time) string {
+	payload := fmt.Sprintf("%d:%s", hotelID, licenseType)
+	if expiresAt != nil {
+		payload += ":" + expiresAt.Format("20060102")
+	}
+	mac := hmac.New(sha256.New, []byte(config.C.License.HMACSecret))
+	mac.Write([]byte(payload))
+	raw := base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(mac.Sum(nil))
+	// 截取前20字符，分4段，每段5字符
+	raw = strings.ToUpper(raw)[:20]
+	return fmt.Sprintf("%s-%s-%s-%s", raw[0:5], raw[5:10], raw[10:15], raw[15:20])
+}
+
+// Activate 激活许可证（绑定设备）
+func (s *LicenseService) Activate(licenseKey, deviceID string) (*model.License, error) {
+	var lic model.License
+	if err := s.db.Where("license_key = ?", licenseKey).First(&lic).Error; err != nil {
+		return nil, ErrLicenseNotFound
+	}
+	if !lic.IsActive {
+		return nil, ErrLicenseInactive
+	}
+	if lic.ExpiresAt != nil && time.Now().After(*lic.ExpiresAt) {
+		return nil, ErrLicenseExpired
+	}
+	// 若已绑定设备，校验是否一致
+	if lic.DeviceID != "" && lic.DeviceID != deviceID {
+		return nil, ErrDeviceMismatch
+	}
+
+	now := time.Now()
+	lic.DeviceID = deviceID
+	lic.ActivatedAt = &now
+	s.db.Save(&lic)
+	return &lic, nil
+}
+
+// Verify 验证（客户端启动时调用）
+func (s *LicenseService) Verify(hotelID uint64, deviceID string) (*model.License, error) {
+	var lic model.License
+	if err := s.db.Where("hotel_id = ? AND device_id = ? AND is_active = 1", hotelID, deviceID).
+		First(&lic).Error; err != nil {
+		return nil, ErrLicenseNotFound
+	}
+	if lic.ExpiresAt != nil && time.Now().After(*lic.ExpiresAt) {
+		return nil, ErrLicenseExpired
+	}
+	return &lic, nil
+}
+
+// Deactivate 解绑设备（换机时使用）
+func (s *LicenseService) Deactivate(hotelID uint64, deviceID string) error {
+	return s.db.Model(&model.License{}).
+		Where("hotel_id = ? AND device_id = ?", hotelID, deviceID).
+		Updates(map[string]interface{}{"device_id": "", "activated_at": nil}).Error
+}