feat(styles): make header css component

apps/ui/src/routes/databases/[id]/__layout.svelte

@@ -150,9 +150,7 @@
 </script>
 
 {#if id !== 'new'}
-	<nav
-		class="flex flex-row px-3 justify-center lg:justify-between items-center bg-neutral-focus lg:fixed w-full z-10 lg:-ml-16 lg:pl-16"
-	>
+	<nav class="header">
 		<div class="hidden items-center space-x-2 p-5 px-6 font-bold lg:flex">
 			<div class="flex flex-col">
 				<div class="md:max-w-64 truncate text-base tracking-tight md:text-2xl lg:block">