feat: 完成 opsx-licence 许可证管理平台全栈实现

基于 opsx-web-lite 框架（Go+Gin+Vue3+Element Plus）构建许可证管理服务器，
业务域参考 Licence 服务器 Web 版。

【后端 - 4层架构】
- 认证：单 Admin 表 + JWT（HS256）
- 核心授权域：Product / Customer / License / Activation
  · License 生成/验证/激活/机器绑定/心跳/续期/吊销
  · 客户端契约接口：/api/v1/license/{verify,activate,deactivate,heartbeat}
- 定价订单：Plan / Order / 支付网关配置
- 防重复购买：CustomerEntitlement + 幂等支付 webhook + 手动发放
- 分析审计：Dashboard 统计 / Analytics / AuditLog / Setting 管理

【前端】
- Dashboard（ECharts 图表）、产品、客户、License、计划、订单、权益、日志、设置
- 9 个完整 CRUD 业务页面 + 登录/布局

【部署】
- SQLite + 单二进制（//go:embed 嵌入前端）
- 开发：./run.sh start（前端5181/后端9001）
- 生产：./run.sh build && ./run.sh binary start
- 默认账号：admin/admin

Author: Logan.Li

backend/internal/service/plan/plan_service.go

@@ -0,0 +1,161 @@
+package plan
+
+import (
+	"backend/internal/dto"
+	"backend/internal/model"
+	"backend/utils"
+	"errors"
+
+	"gorm.io/gorm"
+)
+
+// PlanService 定价计划业务逻辑层 // Logan.Li
+type PlanService struct {
+	db *gorm.DB
+}
+
+// NewPlanService 创建 service 实例 // Logan.Li
+func NewPlanService(db *gorm.DB) *PlanService {
+	return &PlanService{db: db}
+}
+
+// List 分页查询定价计划 // Logan.Li
+func (s *PlanService) List(page, pageSize int, productID uint) ([]dto.PlanResponse, int64, error) {
+	var plans []model.Plan
+	var total int64
+
+	query := s.db.Model(&model.Plan{}).Preload("Product")
+	if productID > 0 {
+		query = query.Where("product_id = ?", productID)
+	}
+
+	query.Count(&total)
+	if err := query.Order("sort_order ASC, created_at DESC").
+		Offset((page - 1) * pageSize).Limit(pageSize).
+		Find(&plans).Error; err != nil {
+		return nil, 0, err
+	}
+
+	results := make([]dto.PlanResponse, 0, len(plans))
+	for _, p := range plans {
+		results = append(results, toPlanResponse(p))
+	}
+	return results, total, nil
+}
+
+// GetByProduct 查询某产品的上架计划（公开接口） // Logan.Li
+func (s *PlanService) GetByProduct(productID uint) ([]dto.PlanResponse, error) {
+	var plans []model.Plan
+	if err := s.db.Where("product_id = ? AND status = ?", productID, 1).
+		Order("sort_order ASC").Find(&plans).Error; err != nil {
+		return nil, errors.New("获取定价计划失败")
+	}
+	results := make([]dto.PlanResponse, 0, len(plans))
+	for _, p := range plans {
+		results = append(results, toPlanResponse(p))
+	}
+	return results, nil
+}
+
+// Create 创建定价计划 // Logan.Li
+func (s *PlanService) Create(req dto.PlanCreate) (*dto.PlanResponse, error) {
+	var product model.Product
+	if err := s.db.First(&product, req.ProductID).Error; err != nil {
+		return nil, errors.New("产品不存在")
+	}
+
+	status := 1
+	if req.Status != nil {
+		status = *req.Status
+	}
+	currency := req.Currency
+	if currency == "" {
+		currency = "USD"
+	}
+
+	plan := model.Plan{
+		ProductID:  req.ProductID,
+		Name:       req.Name,
+		PlanType:   req.PlanType,
+		Price:      req.Price,
+		Currency:   currency,
+		Duration:   req.Duration,
+		MaxDevices: req.MaxDevices,
+		Features:   utils.FormatFeatures(req.Features),
+		SortOrder:  req.SortOrder,
+		Status:     status,
+	}
+	if err := s.db.Create(&plan).Error; err != nil {
+		return nil, errors.New("创建定价计划失败")
+	}
+	resp := toPlanResponse(plan)
+	return &resp, nil
+}
+
+// Update 更新定价计划 // Logan.Li
+func (s *PlanService) Update(id uint, req dto.PlanUpdate) (*dto.PlanResponse, error) {
+	var plan model.Plan
+	if err := s.db.First(&plan, id).Error; err != nil {
+		return nil, errors.New("定价计划不存在")
+	}
+
+	updates := map[string]interface{}{}
+	if req.Name != "" {
+		updates["name"] = req.Name
+	}
+	if req.Price != nil {
+		updates["price"] = *req.Price
+	}
+	if req.Currency != "" {
+		updates["currency"] = req.Currency
+	}
+	if req.Duration != nil {
+		updates["duration"] = *req.Duration
+	}
+	if req.MaxDevices != nil {
+		updates["max_devices"] = *req.MaxDevices
+	}
+	if req.Features != nil {
+		updates["features"] = utils.FormatFeatures(req.Features)
+	}
+	if req.SortOrder != nil {
+		updates["sort_order"] = *req.SortOrder
+	}
+	if req.Status != nil {
+		updates["status"] = *req.Status
+	}
+
+	if err := s.db.Model(&plan).Updates(updates).Error; err != nil {
+		return nil, errors.New("更新定价计划失败")
+	}
+	s.db.First(&plan, id)
+	resp := toPlanResponse(plan)
+	return &resp, nil
+}
+
+// Delete 删除定价计划 // Logan.Li
+func (s *PlanService) Delete(id uint) error {
+	return s.db.Delete(&model.Plan{}, id).Error
+}
+
+// ToggleStatus 切换上下架状态 // Logan.Li
+func (s *PlanService) ToggleStatus(id uint, status int) error {
+	return s.db.Model(&model.Plan{}).Where("id = ?", id).Update("status", status).Error
+}
+
+// toPlanResponse 模型转响应 DTO // Logan.Li
+func toPlanResponse(p model.Plan) dto.PlanResponse {
+	return dto.PlanResponse{
+		ID:         p.ID,
+		ProductID:  p.ProductID,
+		Name:       p.Name,
+		PlanType:   p.PlanType,
+		Price:      p.Price,
+		Currency:   p.Currency,
+		Duration:   p.Duration,
+		MaxDevices: p.MaxDevices,
+		Features:   utils.ParseFeatures(p.Features),
+		SortOrder:  p.SortOrder,
+		Status:     p.Status,
+	}
+}