Stop the "Open Files" button from disappearing at certain zoom levels (#5384)

I have been trying to get this perfect for a while, but this is the best
I can do. I tried to get the open files button to be sticky at the
bottom, but beyond certain zoom levels, this causes it to disappear. Not
worth spending more time on it right now.

Co-authored-by: James Brunton <[email protected]>

frontend/src/core/components/shared/filePreview/DocumentThumbnail.tsx

@@ -41,7 +41,12 @@ const DocumentThumbnail: React.FC<DocumentThumbnailProps> = ({
             src={thumbnail}
             alt={`Preview of ${file.name}`}
             fit="contain"
-            style={{ maxWidth: '100%', maxHeight: '100%' }}
+            style={{ 
+              maxWidth: '100%', 
+              maxHeight: '100%',
+              width: 'auto',
+              height: 'auto'
+            }}
           />
         </PrivateContent>
         {children}