fix: use absolute paths for service worker registration

SvelteKit sets Vite's base to './' for client builds, causing the PWA
plugin to generate relative SW paths (./sw.js). On sub-routes like
/settings or /tag/foo, this resolves to /settings/sw.js which returns
HTML, breaking SW registration. Force scope and buildBase to '/'.

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

vite.config.ts

@@ -23,6 +23,8 @@ export default defineConfig({
 				]
 			: []),
 		SvelteKitPWA({
+			scope: '/',
+			buildBase: '/',
 			registerType: 'autoUpdate',
 			manifest: {
 				name: 'Crumbs by Bretzel',