feat: add modern content and navigation primitives

layouts/partials/header/floating.html

@@ -0,0 +1,6 @@
+<div class="min-h-[104px]"></div>
+<header class="fixed inset-x-0 top-3 z-100 px-3 sm:top-5 sm:px-6">
+  <div class="mx-auto max-w-7xl rounded-2xl border border-neutral-200/80 bg-neutral/85 px-3 shadow-lg shadow-neutral-950/5 backdrop-blur-xl dark:border-neutral-700/80 dark:bg-neutral-800/85">
+    {{ partial "header/basic.html" . }}
+  </div>
+</header>