fix: allow panning in projection view when mouse is outside room boundaries

The background Rect was intercepting mouse events, causing the pan
hit-test to treat it as an interactive item and skip panning. Adding
listening={false} lets clicks pass through to the Stage.

apps/client/src/components/editor/projection/WallProjectionView.tsx

@@ -554,6 +554,7 @@ export function WallProjectionView({
           width={width}
           height={height}
           fill={isHighlighted ? colors.canvasBgHighlight : colors.canvasBg}
+          listening={false}
         />
 
         {/* Pan group: all content shifts with viewPan */}