Fix: Duplicate Thumbnail Images in DICOM Tag Browser

Problem

Thumbnail scale was wrong
After commit 89a62a4, thumbnail images were appearing twice in the DICOM tag browser.

Root Cause

When thumbnail image support was added:

1. THUMBNAIL images were correctly identified and added to both thumbnailImages
   and volumeImages arrays (since they share ImageType VOLUME/THUMBNAIL behavior)
2. The Slide constructor then concatenated both arrays:

   images: [
     ...item.volumeImages,      // Contains thumbnails
     ...item.labelImages,
     ...item.overviewImages,
     ...item.thumbnailImages    // Duplicates the same thumbnails
   ]

Solution

Remove thumbnailImages from the Slide constructor concatenation.
THUMBNAIL images are already included in volumeImages since they:

• Share the same Frame of Reference UID as VOLUME images
• Are part of the same image pyramid structure
• Need to be processed together with VOLUME images

Changes

• src/data/slides.tsx (line ~120): Keep thumbnail images in volumeImages array
• src/data/slides.tsx (line ~357): Remove thumbnailImages from Slide constructor

Result

Thumbnail images now appear only once in the DICOM tag browser while
maintaining their proper relationship with the volume image pyramid.

Ref: #337 (comment)