fix: register PWA service worker via virtual:pwa-register for offline support

@vite-pwa/sveltekit does not auto-inject SW registration into SSR HTML.
Add explicit registration via virtual:pwa-register in root layout onMount,
inject webmanifest link via virtual:pwa-info, disable SvelteKit's built-in
SW registration to avoid conflicts, and add required dependencies.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

svelte.config.js

@@ -5,7 +5,10 @@ const config = {
 	kit: {
 		adapter: adapter({
 			out: 'build'
-		})
+		}),
+		serviceWorker: {
+			register: false
+		}
 	}
 };