feat: expose hotel cost unit and iso country code via the api

The Teamer app groups hotels by cost unit and renders a flag per
destination, and cannot derive either from what /api/hotels returns
today.

costUnit is the raw kostenstelle and stays a string: only 281 of 1931
hotels carry one and some hold a space-separated list such as "84 85".

countryCode goes through CountryCodeMapper, whose table is part of the
API contract: BusPro's land column mixes ISO-2, ISO-3 and European
vehicle registration codes for the same country, and a wrong entry
mislabels a destination's flag silently. An unmappable token is null and
warns on the bpn channel, never a guess. country itself is untouched --
it remains the join key into /api/countries[].token.

Co-Authored-By: Claude Opus 5 <[email protected]>

config/services.yaml

@@ -207,6 +207,10 @@ services:
         arguments:
             $cache: '@bpn.cache'
 
+    App\BusProNet\Utility\CountryCodeMapper:
+        arguments:
+            $logger: '@monolog.logger.bpn'
+
     App\BusProNet\XmlLoader\HotelLoader:
         arguments:
             $cache: '@bpn.cache'