fix: correctly handle discounts applied by dpn api

src/BusProNet/Model/BookingResponse.php

@@ -111,8 +111,12 @@ class BookingResponse
      * - ERM/GRU: Gruppenrabatt (group discount for large bookings)
      * - Other ERM subtypes: Various automatic discounts
      *
-     * These discounts appear as negative price items and must be accounted for when
-     * comparing the API total price against the locally calculated price.
+     * These discounts appear as negative price items with type "ERM" and must be
+     * accounted for when comparing the API total price against the locally calculated price.
+     *
+     * Important: Only ERM type discounts are considered API-applied. Other negative price
+     * items (like BEF transportation discounts) are already handled by the local price
+     * calculator and should not be subtracted again.
      *
      * Note: Voucher discounts (AKTION, KULANZGUTSCHEIN) are handled separately via
      * getVoucherDiscountFromPrices() as they are user-initiated, not automatic.
@@ -123,8 +127,7 @@ class BookingResponse
     {
         return array_filter(
             $this->priceItems,
-            fn (PriceItem $item) => $item->totalPrice < 0
-                && false === \in_array($item->type, ['AKTION', 'KULANZGUTSCHEIN'], true)
+            fn (PriceItem $item) => $item->totalPrice < 0 && 'ERM' === $item->type
         );
     }