feat(hackathon): Improve dark mode and UI/UX in Hackathon website (#64)

* feat: update landing page

* feat: Add favicon and SEO (JSON-LD schema, meta tags)

- Add favicon image
- Add JSON-LD schema for Hackathon event
- Add react-helmet-async for managing meta tags

* chore: remove react-helmet-async

* chore: update landing page

* chore: update UI for signup and login

- add back button for better UX

* feat: add image loading state and skeleton UI for team dashboard

* fix: landing navbar not sticky to top, fix onboarding UI

* feat(hackathon): update UI

- Update dashboard, onboarding user, edit profile, and team layout
  to make it more consistent

* fix: optimize placeholder banner image & minor fix dark mode

* feat(hackathon): update landing page dark mode color scheme

* feat(hackathon): update auth page dark mode color scheme

* feat(hackathon): dashboard UI improvement and dark mode adjustment

* feat(hackathon): browse team page

- update dark mode color scheme
- add some border style to give outline and depth
- change emoji to icon

* feat(hackathon): update team page

- update dark mode color scheme for team page: view, team edit,
  and submit project page
- fix bug in chat where messages are displayed double
- make the form field size consistent

* feat(hackathon): update dark mode onboarding and edit profile

---------

Co-authored-by: Maulana Sodiqin <sodiqincahyana1@gmail.com>
Co-authored-by: Muhammad Zakir Ramadhan <61570975+zakirkun@users.noreply.github.com>

apps/hackathon/src/app/404.tsx

@@ -2,13 +2,13 @@ import { Link } from 'react-router-dom';
 
 export default function NotFoundPage() {
   return (
-    <div className="min-h-screen flex items-center justify-center bg-gray-50">
+    <div className="min-h-screen flex items-center justify-center bg-gray-50 dark:bg-gray-950">
       <div className="text-center">
         <h1 className="text-9xl font-bold text-gray-200 mb-4">404</h1>
-        <h2 className="text-3xl font-semibold text-gray-900 mb-4">
+        <h2 className="text-3xl font-semibold text-gray-900 dark:text-gray-300 mb-4">
           Page Not Found
         </h2>
-        <p className="text-gray-600 mb-8">
+        <p className="text-gray-600 dark:text-gray-400 mb-8">
           The page you are looking for doesn't exist or has been moved.
         </p>
         <Link