feat: render subheadlines as inline markdown

Subheadlines in page headers and post cards support inline markdown
(bold, italic, links) via marked.parseInline.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/components/PostCard.svelte

@@ -8,6 +8,7 @@
   import Card from "./Card.svelte";
   import { getPostEventInfo } from "$lib/blog-utils";
   import { useTranslate, T } from "$lib/translations";
+  import { marked } from "$lib/markdown-safe";
 
   const t = useTranslate();
 
@@ -119,7 +120,7 @@
       </h5>
       {#if post.subheadline}
         <div class="text-xs line-clamp-2 mb-1">
-          {post.subheadline}
+          {@html marked.parseInline(post.subheadline)}
         </div>
       {/if}
       {#if post.excerpt}