fix(image-viewer): pan tracks the cursor 1:1 when zoomed

The timeline image viewer's transform applied translate inside scale(), so
dragging a zoomed image moved it by zoom x the cursor distance (panning outran
the pointer). Divide the pan offset by zoom so it tracks 1:1 - matching the
media-gallery lightbox fix.

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

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

@@ -86,7 +86,12 @@ export const ImageViewer = as<'div', ImageViewerProps>(
             className={css.ImageViewerImg}
             style={{
               cursor,
-              transform: `scale(${zoom}) translate(${pan.translateX}px, ${pan.translateY}px)`,
+              // translate runs inside scale(), so divide by zoom to make a dragged
+              // pixel move the image one screen pixel (1:1 with the cursor) rather
+              // than `zoom` pixels.
+              transform: `scale(${zoom}) translate(${pan.translateX / zoom}px, ${
+                pan.translateY / zoom
+              }px)`,
             }}
             src={src}
             alt={alt}