Allow free zoom and pan in drawing mode

lib/features/sheet_viewer/drawing/drawing_board.dart

@@ -96,18 +96,32 @@ class _DrawingBoardState extends State<DrawingBoard> {
     }
 
     // Drawing mode: wrap with InteractiveViewer for zoom/pan
-    return Align(
+    // Use LayoutBuilder to get available size and center content manually
-      alignment: widget.alignment,
+    return LayoutBuilder(
-      child: InteractiveViewer(
+      builder: (context, constraints) {
-        transformationController: _transformationController,
+        // Calculate padding to center the content
-        minScale: widget.minScale,
+        final horizontalPadding =
-        maxScale: widget.maxScale,
+            (constraints.maxWidth - widget.boardSize.width) / 2;
-        boundaryMargin: EdgeInsets.zero,
+        final verticalPadding =
-        constrained: true,
+            (constraints.maxHeight - widget.boardSize.height) / 2;
-        panEnabled: !_isDrawing,
+
-        scaleEnabled: !_isDrawing,
+        return InteractiveViewer(
-        child: content,
+          transformationController: _transformationController,
-      ),
+          minScale: widget.minScale,
+          maxScale: widget.maxScale,
+          boundaryMargin: const EdgeInsets.all(double.infinity),
+          constrained: false,
+          panEnabled: !_isDrawing,
+          scaleEnabled: !_isDrawing,
+          child: Padding(
+            padding: EdgeInsets.only(
+              left: horizontalPadding > 0 ? horizontalPadding : 0,
+              top: verticalPadding > 0 ? verticalPadding : 0,
+            ),
+            child: content,
+          ),
+        );
+      },
     );
   }