fix: align templates with wireframe styling

- Fix article header tag borders: replace broken border-current/20
  (Tailwind can't apply opacity to currentColor) with per-tag border
  colour classes via new get_tag_border_css filter
- Add calendar icon before article date in article header
- Add clock icon before read time in article header and home featured
- Match article card footer to wireframe (remove extra min-read span)
- Add rounded-md to code block matching wireframe

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

templates/components/article_card.html

@@ -20,12 +20,9 @@
       <h2 class="font-display font-bold text-2xl md:text-3xl mb-3 group-hover:text-brand-cyan transition-colors">{{ article.title }}</h2>
     </a>
     <p class="text-zinc-600 dark:text-zinc-400 mb-6 max-w-2xl line-clamp-2">{{ article.summary }}</p>
-    <div class="flex items-center justify-between mt-auto">
-      <span class="text-sm font-mono text-zinc-500">{{ article.read_time_mins }} min read</span>
-      <a href="{{ article.url }}" class="flex items-center gap-2 text-sm font-bold font-mono group-hover:text-brand-cyan transition-colors">
-        Read Article
-        <svg class="w-4 h-4" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor"><path stroke-linecap="round" stroke-linejoin="round" d="m4.5 19.5 15-15m0 0H8.25m11.25 0v11.25" /></svg>
-      </a>
-    </div>
+    <a href="{{ article.url }}" class="flex items-center gap-2 mt-auto text-sm font-bold font-mono group-hover:text-brand-cyan transition-colors">
+      Read Article
+      <svg class="w-4 h-4" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="2" stroke="currentColor"><path stroke-linecap="round" stroke-linejoin="round" d="m4.5 19.5 15-15m0 0H8.25m11.25 0v11.25" /></svg>
+    </a>
   </div>
 </article>