feat(payment): 发送支付成功通知邮件

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/internal/handler/payment_handler.go

@@ -264,6 +264,7 @@ func (h *PaymentHandler) CreateOrder(c *gin.Context) {
 		PaymentSource:   req.PaymentSource,
 		OrderType:       req.OrderType,
 		PlanID:          req.PlanID,
+		Locale:          c.GetHeader("Accept-Language"),
 	})
 	if err != nil {
 		response.ErrorFrom(c, err)

backend/internal/service/payment_fulfillment.go

@@ -310,9 +310,87 @@ func (s *PaymentService) markCompleted(ctx context.Context, o *dbent.PaymentOrde
 		"creditedAmount": o.Amount,
 		"payAmount":      o.PayAmount,
 	})
+	s.dispatchPaymentFulfillmentNotification(o, auditAction)
 	return nil
 }
 
+func (s *PaymentService) dispatchPaymentFulfillmentNotification(o *dbent.PaymentOrder, auditAction string) {
+	if s == nil || s.notificationEmailService == nil || o == nil {
+		return
+	}
+	go func() {
+		ctx, cancel := context.WithTimeout(context.Background(), emailSendTimeout)
+		defer cancel()
+		var err error
+		switch auditAction {
+		case "RECHARGE_SUCCESS":
+			err = s.sendBalanceRechargeSuccessNotification(ctx, o)
+		case "SUBSCRIPTION_SUCCESS":
+			err = s.sendSubscriptionPurchaseSuccessNotification(ctx, o)
+		default:
+			return
+		}
+		if err != nil {
+			slog.Warn("payment fulfillment notification email failed", "order_id", o.ID, "action", auditAction, "err", err.Error())
+		}
+	}()
+}
+
+func (s *PaymentService) sendBalanceRechargeSuccessNotification(ctx context.Context, o *dbent.PaymentOrder) error {
+	currentBalance := ""
+	if s.userRepo != nil {
+		if user, err := s.userRepo.GetByID(ctx, o.UserID); err == nil && user != nil {
+			currentBalance = fmt.Sprintf("%.2f", user.Balance)
+		}
+	}
+	return s.notificationEmailService.Send(ctx, NotificationEmailSendInput{
+		Event:          NotificationEmailEventBalanceRechargeSuccess,
+		RecipientEmail: o.UserEmail,
+		RecipientName:  firstNonEmpty(o.UserName, o.UserEmail),
+		UserID:         o.UserID,
+		SourceType:     "payment_order",
+		SourceID:       strconv.FormatInt(o.ID, 10),
+		Variables: map[string]string{
+			"recharge_amount": fmt.Sprintf("%.2f", o.Amount),
+			"current_balance": currentBalance,
+			"order_id":        strconv.FormatInt(o.ID, 10),
+		},
+	})
+}
+
+func (s *PaymentService) sendSubscriptionPurchaseSuccessNotification(ctx context.Context, o *dbent.PaymentOrder) error {
+	variables := map[string]string{
+		"subscription_group": "Subscription",
+		"subscription_days":  "",
+		"expiry_time":        "",
+		"order_id":           strconv.FormatInt(o.ID, 10),
+	}
+	if o.SubscriptionDays != nil {
+		variables["subscription_days"] = strconv.Itoa(*o.SubscriptionDays)
+	}
+	if o.SubscriptionGroupID != nil {
+		if s.groupRepo != nil {
+			if group, err := s.groupRepo.GetByID(ctx, *o.SubscriptionGroupID); err == nil && group != nil && strings.TrimSpace(group.Name) != "" {
+				variables["subscription_group"] = group.Name
+			}
+		}
+		if s.subscriptionSvc != nil {
+			if sub, err := s.subscriptionSvc.GetActiveSubscription(ctx, o.UserID, *o.SubscriptionGroupID); err == nil && sub != nil {
+				variables["expiry_time"] = sub.ExpiresAt.Format("2006-01-02 15:04")
+			}
+		}
+	}
+	return s.notificationEmailService.Send(ctx, NotificationEmailSendInput{
+		Event:          NotificationEmailEventSubscriptionPurchaseSuccess,
+		RecipientEmail: o.UserEmail,
+		RecipientName:  firstNonEmpty(o.UserName, o.UserEmail),
+		UserID:         o.UserID,
+		SourceType:     "payment_order",
+		SourceID:       strconv.FormatInt(o.ID, 10),
+		Variables:      variables,
+	})
+}
+
 func (s *PaymentService) ExecuteSubscriptionFulfillment(ctx context.Context, oid int64) error {
 	o, err := s.entClient.PaymentOrder.Get(ctx, oid)
 	if err != nil {

backend/internal/service/payment_order.go

@@ -48,6 +48,9 @@ func (s *PaymentService) CreateOrder(ctx context.Context, req CreateOrderRequest
 	if user.Status != payment.EntityStatusActive {
 		return nil, infraerrors.Forbidden("USER_INACTIVE", "user account is disabled")
 	}
+	if s.notificationEmailService != nil {
+		s.notificationEmailService.RememberRecipientLocale(ctx, req.UserID, user.Email, req.Locale)
+	}
 	orderAmount := req.Amount
 	limitAmount := req.Amount
 	if plan != nil {

backend/internal/service/payment_service.go

@@ -83,6 +83,7 @@ type CreateOrderRequest struct {
 	PaymentSource   string
 	OrderType       string
 	PlanID          int64
+	Locale          string
 }
 
 type CreateOrderResponse struct {
@@ -174,18 +175,19 @@ type TopUserStat struct {
 // --- Service ---
 
 type PaymentService struct {
-	providerMu       sync.Mutex
-	providersLoaded  bool
-	entClient        *dbent.Client
-	registry         *payment.Registry
-	loadBalancer     payment.LoadBalancer
-	redeemService    *RedeemService
-	subscriptionSvc  *SubscriptionService
-	configService    *PaymentConfigService
-	userRepo         UserRepository
-	groupRepo        GroupRepository
-	resumeService    *PaymentResumeService
-	affiliateService *AffiliateService
+	providerMu               sync.Mutex
+	providersLoaded          bool
+	entClient                *dbent.Client
+	registry                 *payment.Registry
+	loadBalancer             payment.LoadBalancer
+	redeemService            *RedeemService
+	subscriptionSvc          *SubscriptionService
+	configService            *PaymentConfigService
+	userRepo                 UserRepository
+	groupRepo                GroupRepository
+	resumeService            *PaymentResumeService
+	affiliateService         *AffiliateService
+	notificationEmailService *NotificationEmailService
 }
 
 func NewPaymentService(entClient *dbent.Client, registry *payment.Registry, loadBalancer payment.LoadBalancer, redeemService *RedeemService, subscriptionSvc *SubscriptionService, configService *PaymentConfigService, userRepo UserRepository, groupRepo GroupRepository, affiliateService *AffiliateService) *PaymentService {
@@ -194,6 +196,10 @@ func NewPaymentService(entClient *dbent.Client, registry *payment.Registry, load
 	return svc
 }
 
+func (s *PaymentService) SetNotificationEmailService(notificationEmailService *NotificationEmailService) {
+	s.notificationEmailService = notificationEmailService
+}
+
 // --- Provider Registry ---
 
 // EnsureProviders lazily initializes the provider registry on first call.