fix(twenty-front): expand HTML preview viewport in DocumentViewer (#23668) (#23676)

## Description
Fixes #23668.

When previewing `.html` or `.htm` files in the file preview modal,
`@cyntler/react-doc-viewer` mounts an `iframe` inside `#html-renderer`.

Previously, `StyledDocumentViewerContainer` applied `height: 100%;
width: 100%;` to `#react-doc-viewer`, `#proxy-renderer`, and
`#msdoc-renderer`, but omitted `#html-renderer` and its inner `iframe`.
As a result, the preview iframe defaulted to inline iframe bounds
instead of expanding to fill the modal container.

This PR adds `#html-renderer`, `#html-renderer iframe`, and `iframe`
selectors to `StyledDocumentViewerContainer`, ensuring HTML previews
expand fully within the modal viewport.

## Testing
- Verified StyledDocumentViewerContainer CSS rules target
`#html-renderer` and `iframe` elements.

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packages/twenty-front/src/modules/activities/files/components/DocumentViewer.tsx

@@ -44,7 +44,10 @@ const StyledDocumentViewerContainer = styled.div`
 
   #react-doc-viewer,
   #proxy-renderer,
-  #msdoc-renderer {
+  #msdoc-renderer,
+  #html-renderer,
+  #html-renderer iframe,
+  iframe {
     background: none;
     display: flex;
     flex-direction: column;