feat(image-viewer): scroll wheel to zoom

The timeline image viewer only zoomed via the -/+ buttons and the % toggle. Add
scroll-to-zoom (wheel up = in, down = out) for parity with the media-gallery
lightbox.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/image-viewer/ImageViewer.tsx

@@ -81,6 +81,10 @@ export const ImageViewer = as<'div', ImageViewerProps>(
           className={css.ImageViewerContent}
           justifyContent="Center"
           alignItems="Center"
+          onWheel={(evt) => {
+            if (evt.deltaY < 0) zoomIn();
+            else if (evt.deltaY > 0) zoomOut();
+          }}
         >
           <img
             className={css.ImageViewerImg}