fix: stop offering unbookable services in the booking edit flow

src/BusProNet/Model/Booking.php

@@ -143,6 +143,31 @@ class Booking
         });
     }
 
+    /**
+     * Checks whether a participant already holds a service in this booking.
+     *
+     * This is the BusPro-side baseline, not the working edit selection: it answers
+     * "did the participant have this service when the booking was last read back".
+     * Services already held may be kept regardless of their current status or
+     * contingent - withdrawing one produces "Anzahl Leistung stimmt nicht mit
+     * Teilnehmerzuordnung überein" on the next update.
+     *
+     * @param int $participantIndex The participant index to search for
+     * @param int $serviceId        The service ID to look for
+     *
+     * @return bool True if the participant already holds the service
+     */
+    public function hasServiceForParticipant(int $participantIndex, int $serviceId): bool
+    {
+        foreach ([...$this->additionalServices, ...$this->transportationServices] as $service) {
+            if ($service->id === $serviceId && in_array($participantIndex, $service->mapping)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * Retrieves transportation service for a specific participant and direction.
      *

src/BusProNet/XmlLoader/TravelLoader.php

@@ -281,9 +281,9 @@ class TravelLoader extends AbstractLoader
     /**
      * Apply availability data to travel services.
      *
-     * Updates the availability status of additional and transportation
-     * services, and the allowed booking status, based on the provided
-     * availability data.
+     * Updates the remaining contingent and the live status of additional and
+     * transportation services, and the allowed booking status, based on the
+     * provided availability data.
      *
      * @param Travel                      $travel         The travel object to update
      * @param ServiceAvailabilityResponse $availabilities The availability data for services
@@ -293,8 +293,19 @@ class TravelLoader extends AbstractLoader
         $serviceAvailabilities = $availabilities->getServices();
 
         foreach ([...$travel->additionalServices, ...$travel->transportationServices] as $service) {
-            if (array_key_exists($service->id, $serviceAvailabilities)) {
-                $service->available = $serviceAvailabilities[$service->id]->available;
+            if (false === array_key_exists($service->id, $serviceAvailabilities)) {
+                continue;
+            }
+
+            $availability = $serviceAvailabilities[$service->id];
+            $service->available = $availability->available;
+
+            // The live status is the only signal that a contingent has run out: BusPro moves a
+            // Leistung to 'Anfrage' without necessarily reporting frei="0". Only overwrite when the
+            // response actually carries one, so a response that omits the attribute does not wipe
+            // the value parsed from the XML export. Mirrors TravelSnapshotManager::applyExtendedToService().
+            if (null !== $availability->status && '' !== trim($availability->status)) {
+                $service->status = $availability->status;
             }
         }