Update site navigation and header styling

The styling for various components including site navigation and the site header has been updated. Changes include amendments to layout options, color, spacing, and border adaptations to provide better visibility and user interaction. The shadow on the top loading bar indicator has also been relocated to enhance the bar's visibility.

apps/web/app/(marketing)/_components/site-header.tsx

@@ -1,21 +1,28 @@
 import type { User } from '@supabase/supabase-js';
 
-import { SiteHeaderAccountSection } from '~/(marketing)/_components/site-header-account-section';
-import { SiteNavigation } from '~/(marketing)/_components/site-navigation';
 import { AppLogo } from '~/components/app-logo';
 
+import { SiteHeaderAccountSection } from './site-header-account-section';
+import { SiteNavigation } from './site-navigation';
+
 export function SiteHeader(props: { user?: User | null }) {
   return (
-    <div className={'border-b border-gray-100 dark:border-border'}>
+    <div
+      className={
+        'sticky top-0 z-10 w-full bg-background/80 shadow-sm backdrop-blur-md dark:bg-background/50 dark:shadow-primary/20'
+      }
+    >
       <div className={'px-4 lg:px-8'}>
-        <div className="flex h-14 items-center justify-between">
-          <div className={'flex w-6/12 items-center space-x-8'}>
+        <div className="grid h-14 grid-cols-3 items-center">
+          <div>
             <AppLogo />
+          </div>
 
+          <div className={'order-first md:order-none'}>
             <SiteNavigation />
           </div>
 
-          <div className={'flex flex-1 items-center justify-end space-x-1'}>
+          <div className={'flex items-center justify-end space-x-1'}>
             <SiteHeaderAccountSection user={props.user ?? null} />
           </div>
         </div>