feat: add a book by scanning

lib/utils/overlay_boundary.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+
+class OverlayBoundary extends StatefulWidget {
+  const OverlayBoundary({super.key, required this.child});
+
+  final Widget child;
+
+  @override
+  State<OverlayBoundary> createState() => _OverlayBoundaryState();
+}
+
+class _OverlayBoundaryState extends State<OverlayBoundary> {
+  late final OverlayEntry _overlayEntry = OverlayEntry(
+    builder: (context) => widget.child,
+  );
+
+  @override
+  void didUpdateWidget(covariant OverlayBoundary oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    _overlayEntry.markNeedsBuild();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Overlay(initialEntries: [_overlayEntry]);
+  }
+}