[APP-2160] Fix PublicationEmbed hero image width on web

The inner View inside the article-region Link was missing `a.w_full`, so on
web (where Link renders as an inline <a>) it shrink-wrapped to the Image's
intrinsic width. Images with small intrinsic dimensions (Leaflet thumbnails)
rendered tiny, while large ones (PCKT) rendered correctly by accident.

The legacy ExternalEmbed sets `a.w_full` on the equivalent View directly
inside the Link wrapper; matching that pattern here.

src/components/Post/Embed/ExternalEmbed/PublicationEmbed/index.tsx

@@ -64,6 +64,7 @@ export function PublicationEmbed({
           <View
             style={[
               a.flex_col,
+              a.w_full,
               a.transition_color,
               hovered ? t.atoms.bg_contrast_25 : null,
             ]}>