Add initlal service-worker with basic offline handling. Manifest is not yet present.

src/routes/+layout.svelte

@@ -2,9 +2,9 @@
 	import { page } from '$app/state';
 	import { slide, fade } from 'svelte/transition';
 	import { onMount } from 'svelte';
+	import { browser } from '$app/environment';
 	import { navigating } from '$app/state';
 	import { LOCATIONS } from '$lib/locations-object.svelte';
-	import { nearestStationsState } from '$lib/geohash.svelte';
 
 	import Loading from '$lib/components/ui/Loading.svelte';
 	import TimezoneWarning from '$lib/components/ui/TimezoneWarning.svelte';
@@ -17,7 +17,19 @@
 
 	import { IconHome, IconDialpad, IconSettings, IconHelp, IconDots } from '@tabler/icons-svelte';
 
-	onMount(() => LOCATIONS.init());
+	onMount(async () => {
+		LOCATIONS.init();
+		if (browser && 'serviceWorker' in navigator) {
+			try {
+				const registration = await navigator.serviceWorker.register('/service-worker.js', {
+					type: 'module',
+				});
+				console.info('OwlBoard Service Worker registered', registration.scope);
+			} catch (error) {
+				console.error('Service Worker installation failed: ', error)
+			}
+		}
+	});
 
 	let { children } = $props();