Fix banquet mode ignored on web: use latest onScan in camera loop

The web scanner's camera loop starts once in useEffect and closed over the
mount-time onScan handler, so switching modes (e.g. to Banquet) kept invoking
the original ticket-check-in handler. Route onScan through a ref updated each
render so the loop always calls the current handler. Native was unaffected.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/components/QRScanner.web.tsx

@@ -10,11 +10,16 @@ export default function QRScanner({ onScan, active }: QRScannerProps) {
   const streamRef = useRef<MediaStream | null>(null);
   const rafRef = useRef<number | null>(null);
   const activeRef = useRef(active);
+  // Route onScan through a ref so the long-lived camera loop (started once in
+  // useEffect) always calls the LATEST handler — otherwise a mode switch
+  // (e.g. to Banquet) keeps hitting the mount-time handler.
+  const onScanRef = useRef(onScan);
   const lastScan = useRef<{ code: string; at: number }>({ code: "", at: 0 });
   const [error, setError] = useState<string | null>(null);
   const [starting, setStarting] = useState(true);
 
   activeRef.current = active;
+  onScanRef.current = onScan;
 
   async function start() {
     setError(null);
@@ -45,7 +50,7 @@ export default function QRScanner({ onScan, active }: QRScannerProps) {
             const now = Date.now();
             if (!(data === lastScan.current.code && now - lastScan.current.at < 3000)) {
               lastScan.current = { code: data, at: now };
-              onScan(data);
+              onScanRef.current(data);
             }
           }
         } catch {