[APP-2160] Apply Figma typography + spacing tweaks to PublicationEmbed

PublicationFooter:
- Avatar to text gap: 10
- Title to author gap: 2
- Title weight medium (500) instead of semi-bold (600)

PublicationEmbed content block:
- Description to meta-row gap: 6 (was 8)
- Divider gets 12px vertical padding wrapper

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

@@ -39,18 +39,18 @@ export function PublicationFooter({
       style={[
         a.flex_row,
         a.align_center,
-        a.gap_sm,
         a.px_md,
         a.py_sm,
         a.transition_color,
+        {gap: 10},
         hovered ? t.atoms.bg_contrast_25 : null,
       ]}
       testID="publication-embed-footer">
       <UserAvatar type="user" size={40} avatar={source.icon} />
-      <View style={[a.flex_1, {minWidth: 0}]}>
+      <View style={[a.flex_1, {minWidth: 0, gap: 2}]}>
         <Text
           numberOfLines={1}
-          style={[a.text_sm, a.font_semi_bold, t.atoms.text]}>
+          style={[a.text_sm, a.font_medium, t.atoms.text]}>
           {name}
         </Text>
         {handle && (

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

@@ -76,7 +76,7 @@ export function PublicationEmbed({
                 loading="lazy"
               />
             ) : null}
-            <View style={[a.p_md, a.gap_sm]}>
+            <View style={[a.p_md, {gap: 6}]}>
               <View style={[{gap: 4}]}>
                 <Text
                   emoji
@@ -103,7 +103,9 @@ export function PublicationEmbed({
           </View>
         )}
       </Link>
-      <Divider />
+      <View style={[a.py_md]}>
+        <Divider />
+      </View>
       <PublicationFooter source={source} />
       {/*
         Note: `source.theme` (background/foreground/accent/accentForeground