Add Electron desktop shell

src/main.ts

@@ -22,7 +22,7 @@ app.mount('#app')
 // In Chrome/Edge, an installed PWA runs in standalone display mode,
 // which removes the top-edge "exit fullscreen" indicator that tabs
 // show when the Fullscreen API is active.
-if ('serviceWorker' in navigator) {
+if ('serviceWorker' in navigator && !window.ruwioDesktop) {
   window.addEventListener('load', () => {
     navigator.serviceWorker.register('/sw.js').catch(() => {
       /* registration failed — app still works without PWA install */

src/types/desktop.d.ts

@@ -0,0 +1,14 @@
+export {}
+
+declare global {
+  interface Window {
+    ruwioDesktop?: {
+      platform: 'aix' | 'android' | 'darwin' | 'freebsd' | 'haiku' | 'linux' | 'openbsd' | 'sunos' | 'win32' | 'cygwin' | 'netbsd'
+      versions: {
+        electron?: string
+        chrome?: string
+        node?: string
+      }
+    }
+  }
+}