pwa: service worker for offline + installerbar (vite-pwa, autoUpdate)

@vite-pwa/astro genererer en Workbox-SW der precacher alt (59 entries); autoUpdate + skipWaiting + cleanupOutdatedCaches saa redeploy aldrig strander en bruger paa gammel version. Registrering injiceret via /registerSW.js i Base.astro (manifest:false bruger den eksisterende site.webmanifest). Offline-brug + Add-to-Home-Screen.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/layouts/Base.astro

@@ -40,6 +40,9 @@ const { title, description, image, type, publishedTime, modifiedTime, tags, json
     </script>
     <Head {title} {description} {image} {type} {publishedTime} {modifiedTime} {tags} {jsonLd} />
     <ClientRouter />
+    <!-- Registrér service worker'en (PWA/offline). Genereret af @vite-pwa i build;
+         is:inline + public-sti så Astro ikke bundler den. 404 i dev = harmløst. -->
+    <script is:inline src="/registerSW.js"></script>
   </head>
   <body class="min-h-screen flex flex-col antialiased">
     <Header />