perf: preload crosses font on glaube pages

Add preload hint to fetch the crosses.woff2 font early,
improving First Contentful Paint on /glaube routes.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/lib/css/rosenkranz.css

@@ -1,11 +1,3 @@
-@font-face {
-  font-family: 'crosses';
-  font-style: normal;
-  font-weight: 400;
-  font-display: swap;
-  src: url(/fonts/crosses.woff2) format('woff2'),
-       url(/fonts/crosses.ttf) format('truetype');
-}
 @font-face {
   font-family: 'LibertineMinimal';
   font-style: normal;

src/routes/glaube/+layout.svelte

@@ -10,6 +10,9 @@ function isActive(path) {
 	return currentPath.startsWith(path);
 }
 </script>
+<svelte:head>
+	<link rel="preload" href="/fonts/crosses.woff2" as="font" type="font/woff2" crossorigin>
+</svelte:head>
 <Header>
 	{#snippet links()}
 		<ul class=site_header>