新功能(#76): 促销系统下单流程集成

- 新增促销规则/规格促销价/使用记录模型与幂等迁移
- EvaluatePromo 支持 new_user/inactive_user/campaign 规则判定
- purchase/preCreate 接入促销判定：命中促销时跳过百分比折扣
- activate 激活后按 order_no 幂等写入 promo_usage
- 订单模型和响应结构新增 promo_rule_id、promo_discount 字段

Co-authored-by: multica-agent <github@multica.ai>

internal/logic/public/order/promoPricing_test.go

@@ -0,0 +1,113 @@
+package order
+
+import (
+	"context"
+	"testing"
+
+	"github.com/perfect-panel/server/internal/model/promo"
+	"github.com/perfect-panel/server/internal/svc"
+	"github.com/perfect-panel/server/internal/types"
+	"gorm.io/gorm"
+)
+
+type fakePromoModel struct {
+	rules []*promo.RuleWithPrice
+}
+
+func (m fakePromoModel) QueryEligibleRules(context.Context, int64) ([]*promo.RuleWithPrice, error) {
+	return m.rules, nil
+}
+
+func (m fakePromoModel) InsertUsage(context.Context, *promo.Usage, ...*gorm.DB) error {
+	return nil
+}
+
+func TestCalculatePurchasePricePromoSkipsPercentDiscount(t *testing.T) {
+	svcCtx := &svc.ServiceContext{
+		DB: &gorm.DB{},
+		PromoModel: fakePromoModel{rules: []*promo.RuleWithPrice{
+			{
+				Rule: promo.Rule{
+					Id:      9,
+					Name:    "campaign",
+					Type:    promo.RuleTypeCampaign,
+					Enabled: true,
+				},
+				PromoPrice: 600,
+			},
+		}},
+	}
+
+	result, err := calculatePurchasePrice(
+		context.Background(),
+		svcCtx,
+		1,
+		2,
+		1000,
+		3,
+		[]types.SubscribeDiscount{{Quantity: 3, Discount: 50}},
+		true,
+		true,
+	)
+	if err != nil {
+		t.Fatalf("calculatePurchasePrice returned error: %v", err)
+	}
+
+	if result.OriginalPrice != 3000 {
+		t.Fatalf("OriginalPrice = %d, want 3000", result.OriginalPrice)
+	}
+	if result.PayableBase != 1800 {
+		t.Fatalf("PayableBase = %d, want 1800", result.PayableBase)
+	}
+	if result.DiscountAmount != 0 {
+		t.Fatalf("DiscountAmount = %d, want 0", result.DiscountAmount)
+	}
+	if result.PromoRuleId != 9 {
+		t.Fatalf("PromoRuleId = %d, want 9", result.PromoRuleId)
+	}
+	if result.PromoDiscount != 1200 {
+		t.Fatalf("PromoDiscount = %d, want 1200", result.PromoDiscount)
+	}
+}
+
+func TestCalculatePurchasePriceIgnoresInvalidPromoPrice(t *testing.T) {
+	svcCtx := &svc.ServiceContext{
+		DB: &gorm.DB{},
+		PromoModel: fakePromoModel{rules: []*promo.RuleWithPrice{
+			{
+				Rule: promo.Rule{
+					Id:      10,
+					Name:    "invalid campaign",
+					Type:    promo.RuleTypeCampaign,
+					Enabled: true,
+				},
+				PromoPrice: 1000,
+			},
+		}},
+	}
+
+	result, err := calculatePurchasePrice(
+		context.Background(),
+		svcCtx,
+		1,
+		2,
+		1000,
+		3,
+		[]types.SubscribeDiscount{{Quantity: 3, Discount: 50}},
+		true,
+		true,
+	)
+	if err != nil {
+		t.Fatalf("calculatePurchasePrice returned error: %v", err)
+	}
+
+	if result.PayableBase != 1500 {
+		t.Fatalf("PayableBase = %d, want 1500", result.PayableBase)
+	}
+	if result.DiscountAmount != 1500 {
+		t.Fatalf("DiscountAmount = %d, want 1500", result.DiscountAmount)
+	}
+	if result.PromoRuleId != 0 || result.PromoDiscount != 0 {
+		t.Fatalf("promo fields = (%d, %d), want (0, 0)", result.PromoRuleId, result.PromoDiscount)
+	}
+}