camera and gallery image crop

mobile-client/src/ScannerView.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useRef, useState } from 'react';
+import { pushOverlayBack } from './platform.js';
 import type { ScanResult } from './scanner.js';
 import { Icon } from './ui.js';
 
@@ -10,6 +11,10 @@ export function ScannerView({ formats, hint, onResult, onClose }: { formats: For
   const [error, setError] = useState<string>();
   const onResultRef = useRef(onResult);
   onResultRef.current = onResult;
+  // Android back button closes the scanner, not the screen underneath.
+  const closeRef = useRef(onClose);
+  closeRef.current = onClose;
+  useEffect(() => pushOverlayBack(closeRef), []);
 
   useEffect(() => {
     let stopped = false;