Show UPRN on selected address in remote assessment

Display the UPRN beneath the selected address on the remote assessment
page so it's available for quicker debugging. The value is already on
the selected address object from the postcode lookup; it just wasn't
rendered.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/portfolio/[slug]/remote-assessment/AddressSearch.tsx

@@ -172,6 +172,9 @@ export default function AddressSearch({
             <p className="text-gray-700 text-sm break-words">
               {selectedAddress.address}
             </p>
+            <p className="text-gray-400 text-xs mt-1 font-mono break-words">
+              UPRN: {selectedAddress.uprn}
+            </p>
           </div>
           <div className="flex justify-end mt-4">
             <Button