refactor: extract reusable library

- move reusable domain, data, state, ui code into src/lib
- update host screens to consume new library exports
- document architecture and configure path aliases
- bump astro integration dependencies for compatibility

Refs #30

src/components/GameDetail.tsx

@@ -1,7 +1,7 @@
 import { h } from 'preact';
 import { useState } from 'preact/hooks';
 import styles from './GameDetail.module.css';
-import type { Game, EndlosGame } from '../types/game';
+import type { Game, EndlosGame } from '@lib/domain/types';
 
 interface GameDetailProps {
   game: Game | undefined;