feat(server-go): 耗材管理（库存/预警/采购建议，#16）

server-go/internal/model/consumable.go

@@ -0,0 +1,45 @@
+package model
+
+import (
+	"math"
+	"time"
+)
+
+// Consumable 耗材
+type Consumable struct {
+	ID          string     `gorm:"type:uuid;primaryKey;default:gen_random_uuid()" json:"id"`
+	Name        string     `gorm:"size:64" json:"name"`
+	Category    string     `gorm:"size:32;index" json:"category"` // lamp_reagent/lamp_consumable/disinfectant/other
+	Spec        *string    `gorm:"size:128" json:"spec,omitempty"`
+	Quantity    float64    `gorm:"type:float" json:"quantity"`
+	Unit        *string    `gorm:"size:32" json:"unit,omitempty"`
+	MinQuantity float64    `gorm:"column:min_quantity;type:float" json:"minQuantity"`
+	ExpiryDate  *time.Time `gorm:"column:expiry_date;type:timestamptz" json:"expiryDate,omitempty"`
+	Supplier    *string    `gorm:"size:128" json:"supplier,omitempty"`
+	Note        *string    `gorm:"type:text" json:"note,omitempty"`
+	CreatedAt   time.Time  `gorm:"type:timestamptz" json:"createdAt"`
+	UpdatedAt   time.Time  `gorm:"type:timestamptz" json:"updatedAt"`
+}
+
+func (Consumable) TableName() string { return "consumables" }
+
+// LowStockAlert 库存低于安全阈值
+func (c Consumable) LowStockAlert() bool {
+	return c.Quantity < c.MinQuantity
+}
+
+// ExpiringAlert 效期在 days 天内到期（含已过期）
+func (c Consumable) ExpiringAlert(days int) bool {
+	if c.ExpiryDate == nil {
+		return false
+	}
+	return !c.ExpiryDate.After(time.Now().Add(time.Duration(days) * 24 * time.Hour))
+}
+
+// PurchaseSuggestion 建议采购量（低于安全阈值时补足差额，向上取整）
+func (c Consumable) PurchaseSuggestion() float64 {
+	if !c.LowStockAlert() {
+		return 0
+	}
+	return math.Ceil(c.MinQuantity - c.Quantity)
+}