fix(payments): stop doubling the pack size in buyer mail

Catalog titles already name the pack ("50 фишек"), so appending the chip count
produced "50 фишек — 50 фишек, 79.00 ₽". The letter now carries the title
exactly as the storefront shows it, then the price.

The tax receipt is unaffected: it states the quantity in the wording the tax
service wants, which is a separate surface with separate requirements.

backend/internal/mynalogsync/mailer.go

@@ -185,15 +185,18 @@ func (m *Mailer) stampReceipt(ctx context.Context, mark func(context.Context, uu
 	}
 }
 
-// describe renders what was bought in one line.
-func describe(title string, chips int, amountMinor int64, currency string) string {
+// describe renders what was bought in one line: the catalog title exactly as the buyer saw it on
+// the storefront, then the price.
+//
+// The pack size is deliberately NOT appended. Catalog titles already name it ("50 фишек"), so
+// adding it produced "50 фишек — 50 фишек". The title is the single source of that wording; the
+// tax receipt states the quantity separately in the form the tax service wants (see
+// mynalog.IncomeName), which is a different surface with different requirements.
+func describe(title string, amountMinor int64, currency string) string {
 	what := strings.TrimSpace(title)
 	if what == "" {
 		what = "покупка в игре"
 	}
-	if chips > 0 {
-		what = fmt.Sprintf("%s — %d фишек", what, chips)
-	}
 	return fmt.Sprintf("%s, %s", what, formatAmount(amountMinor, currency))
 }
 
@@ -224,7 +227,7 @@ func purchaseText(p payments.PurchaseMail) string {
 отдельным письмом: обычно в течение часа, но иногда это занимает до нескольких дней.
 
 Спасибо, что играете в «Эрудит».
-`, describe(p.Title, p.Chips, p.AmountMinor, p.Currency), p.OrderID)
+`, describe(p.Title, p.AmountMinor, p.Currency), p.OrderID)
 }
 
 // receiptText is the fiscal receipt letter, which is how the receipt is actually handed to the
@@ -240,7 +243,7 @@ func receiptText(r payments.ReceiptMail, inn, baseURL string, loc *time.Location
 
 Продавец применяет налог на профессиональный доход; чек сформирован в сервисе
 «Мой налог» Федеральной налоговой службы.
-`, describe(r.Title, r.Chips, r.AmountMinor, r.Currency),
+`, describe(r.Title, r.AmountMinor, r.Currency),
 		r.OperationTime.In(loc).Format("02.01.2006 15:04"),
 		mynalog.ReceiptURL(baseURL, inn, r.ReceiptUUID))
 }
@@ -255,6 +258,6 @@ func cancelText(r payments.ReceiptMail, loc *time.Location) string {
 
 %s
 Дата покупки: %s
-`, describe(r.Title, r.Chips, r.AmountMinor, r.Currency),
+`, describe(r.Title, r.AmountMinor, r.Currency),
 		r.OperationTime.In(loc).Format("02.01.2006 15:04"))
 }