feat: make boarding point price levelling switchable

.env

@@ -92,6 +92,15 @@ APP_TRAVEL_PREFER_REMOTE=false
 APP_TRAVEL_ENABLE_FALLBACK=true
 APP_TRAVEL_SNAPSHOT_RETENTION_BUFFER_DAYS=14
 
+# Compensates a BusPro export defect: a <zustieg_rueck> can omit its preis although the booking
+# engine still bills the return-leg Abfahrtsortzuschlag, so we undercharge by exactly one leg.
+# A boarding point costs the same in both directions, so the stated price is applied to both.
+# Off = report the export verbatim. Provisional until the vendor fixes the export; see
+# docs/buspro-database-reference.md section A7.
+# Flipping this needs `app:bpn:xml-cache-invalidate` and `app:bpn:refresh-travel-snapshot`,
+# because the cached travels and TravelSnapshot rows carry the parsed price.
+APP_BPN_LEVEL_BOARDING_POINT_PRICES=true
+
 # Emails
 APP_DEFAULT_EMAIL_FROM=[email protected]
 APP_DEFAULT_EMAIL_TO=[email protected]