Use drawing controller

lib/features/sheet_viewer/widgets/paint_mode_layer.dart

@@ -6,13 +6,15 @@ import 'pdf_page_display.dart';
 /// Drawing overlay for annotating PDF pages.
 ///
 /// Uses flutter_drawing_board to provide a paint canvas over the PDF.
-/// Only available in single-page mode.
+/// Only working in single-page mode.
 class PaintModeLayer extends StatelessWidget {
   final PdfPageDisplay pageDisplay;
+  final DrawingController drawingController;
 
   const PaintModeLayer({
     super.key,
     required this.pageDisplay,
+    required this.drawingController,
   });
 
   @override
@@ -24,6 +26,7 @@ class PaintModeLayer extends StatelessWidget {
           final (pageSize, _) = pageDisplay.calculateScaledPageSizes(maxSize);
 
           return DrawingBoard(
+            controller: drawingController,
             background: SizedBox(
               width: pageSize.width,
               height: pageSize.height,