fix(payments): a console refund that its own notification beat is not a repeat

Refunding from /_gm reported "Already refunded" for a refund that had just
succeeded, which reads as "you clicked twice".

The two recording paths race. YooKassa fires refund.succeeded the moment
POST /v3/refunds returns, so the notification handler often writes the reversal
before the console's own write lands. Both name the same refund id, so the
ledger's idempotency index rejects the second — which is the mechanism working
exactly as intended: on the contour the money moved once, one refund row was
written, the balance is right and no abuse flag was raised. Only the message
was wrong about why.

The console now reports success on that path, and the notification's log line
no longer claims the refund was "issued outside the console" when it may well
have come from it.

Covered by an integration test that lands the notification first and then
refunds from the console, asserting the operator is told it succeeded and that
exactly one refund row exists.

backend/internal/server/handlers_yookassa.go

@@ -282,7 +282,10 @@ func (s *Server) handleYooKassaRefundNotification(c *gin.Context, note yookassa.
 		return
 	}
 	if !out.AlreadyRefunded {
-		s.log.Info("yookassa refund notify: reversed a refund issued outside the console",
+		// This is the first record of the refund. It is usually one an operator made in the merchant
+		// cabinet, but it can equally be a console refund whose notification outran the console's own
+		// write — both name the same refund id, so either way it is recorded exactly once.
+		s.log.Info("yookassa refund notify: reversed a refund",
 			zap.String("order", ref.OrderID.String()), zap.String("refund", refund.ID),
 			zap.Int("revoked", out.Revoked), zap.Int("loss", out.Loss))
 	}