When a flagged wash has no metadata in the api flag-context payload, the user previously saw 'No XL Vask details available.' with no indication of why. This adds a clearer fallback message and adds unit coverage for that scenario. Resolves TRU-8 (AUT-4). Co-authored-by: Jeppe <jeppe@copenhagentruckwash.io> Co-authored-by: openhands <openhands@all-hands.dev>