Migrate Tír na nÓg landing page to Next.js

Summary of changes:
- Created the 'feature/migration-nextjs' branch.
- Initialized a Next.js project with React components and App Router structure.
- Created reusable UI components: Viewport, World, Room, and Door in 'app/components/'.
- Implemented spatial navigation logic (WASD/Arrows and clicks) using React 'useState' and 'useEffect' in 'app/page.js'.
- Migrated the Tír na nÓg pixel-art aesthetic and layout transitions into 'app/globals.css'.
- Configured a Gitea Runner CI/CD workflow in '.gitea/workflows/deploy.yml' for automated builds and linting.
- Added a '.gitignore' file to manage project artifacts.

Co-authored-by: micmug <185775013+micmug@users.noreply.github.com>

app/components/Viewport.js

@@ -0,0 +1,3 @@
+export default function Viewport({ children }) {
+  return <div id="viewport">{children}</div>;
+}