feat: installable PWA (manifest, icons, minimal service worker)

- public/manifest.webmanifest with any + maskable icons (192/512)
- generated inbox-glyph icons in app palette, apple-touch-icon
- minimal no-cache service worker for installability; registered via client plugin
- head: manifest/icon links, mobile-web-app-capable

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nuxt.config.ts

@@ -23,11 +23,15 @@ export default defineNuxtConfig({
         { name: "color-scheme", content: "light dark" },
         { name: "theme-color", media: "(prefers-color-scheme: light)", content: "#f4f1ea" },
         { name: "theme-color", media: "(prefers-color-scheme: dark)", content: "#181410" },
+        { name: "mobile-web-app-capable", content: "yes" },
         { name: "apple-mobile-web-app-capable", content: "yes" },
         { name: "apple-mobile-web-app-status-bar-style", content: "default" },
         { name: "apple-mobile-web-app-title", content: "ClaudeDo" },
       ],
       link: [
+        { rel: "manifest", href: "/manifest.webmanifest" },
+        { rel: "apple-touch-icon", href: "/icons/apple-touch-icon.png" },
+        { rel: "icon", type: "image/png", sizes: "192x192", href: "/icons/icon-192.png" },
         { rel: "preconnect", href: "https://fonts.googleapis.com" },
         { rel: "preconnect", href: "https://fonts.gstatic.com", crossorigin: "" },
         {