feat: add zachleat.com-inspired theme enhancements

- Add time-difference web component for relative dates
- Add @zachleat/table-saw for responsive tables
- Add webmention facepile styling with bookmarks support
- Add OG image thumbnails to post navigation
- Add @11ty/is-land for lazy widget hydration
- Wrap sidebar widgets in is-land for deferred loading
- Lazy-load webmention avatars with is-land
- Add @zachleat/filter-container for blog archive filtering
- Add posting frequency sparkline to blog header
- Inline critical CSS and defer full stylesheet loading

_includes/components/widgets/funkwhale.njk

@@ -1,5 +1,6 @@
 {# Funkwhale Now Playing Widget #}
 {% if funkwhaleActivity and (funkwhaleActivity.nowPlaying or funkwhaleActivity.stats) %}
+<is-land on:visible>
 <div class="widget">
   <h3 class="widget-title flex items-center gap-2">
     <svg class="w-5 h-5 text-purple-500" fill="none" stroke="currentColor" viewBox="0 0 24 24">
@@ -68,4 +69,5 @@
     <svg class="w-3 h-3" fill="none" stroke="currentColor" viewBox="0 0 24 24"><path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 5l7 7-7 7"/></svg>
   </a>
 </div>
+</is-land>
 {% endif %}