[APP-2160] Flush divider; move footer vertical padding to py_md

Previously the divider's own py_md wrapper plus the footer's py_sm
double-counted the spacing and pushed the footer further from the
divider than Figma. Make the divider flush against the article block
and the footer, and bump the footer to py_md so the 12px gap below
the divider line is owned by the footer itself.

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

@@ -40,7 +40,7 @@ export function PublicationFooter({
         a.flex_row,
         a.align_center,
         a.px_md,
-        a.py_sm,
+        a.py_md,
         a.transition_color,
         {gap: 10},
         hovered ? t.atoms.bg_contrast_25 : null,

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

@@ -103,9 +103,7 @@ export function PublicationEmbed({
           </View>
         )}
       </Link>
-      <View style={[a.py_md]}>
-        <Divider />
-      </View>
+      <Divider />
       <PublicationFooter source={source} />
       {/*
         Note: `source.theme` (background/foreground/accent/accentForeground