feat: Electron desktop app — hardening, IPC bridge, and dev launch fixes

- Dev/prod URL auto-detection (Vite 5173 in dev, server 3000 in prod)
- Typed IPC bridge via preload (notifications, badge, window controls, updates, deep links)
- Native OS notifications via NotificationController with window focus suppression
- Auto-update via electron-updater with UpdateToast UI
- Deep linking (backspace:// protocol) for macOS and Windows/Linux
- Window state persistence (position, size, maximize across restarts)
- Tray icon with graceful fallback when icon asset missing
- Suppress PWA service worker polling/reloads inside Electron
- Platform detection layer (isElectron, getElectronAPI)
- Root workspace scripts (dev:desktop, build:desktop)
- Document BACKSPACE_URL and BACKSPACE_UPDATE_URL env vars

packages/web/src/components/ui/SwUpdatePrompt.tsx

@@ -1,10 +1,13 @@
 import { useRegisterSW } from 'virtual:pwa-register/react';
 import { useEffect } from 'react';
+import { isElectron } from '../../platform/platform';
 
 export function SwAutoUpdate() {
+  const inElectron = isElectron();
+
   useRegisterSW({
     onRegisteredSW(_swUrl, registration) {
-      if (!registration) return;
+      if (!registration || inElectron) return;
       setInterval(() => {
         registration.update();
       }, 60_000);
@@ -12,11 +15,12 @@ export function SwAutoUpdate() {
   });
 
   useEffect(() => {
+    if (inElectron) return;
     if (!navigator.serviceWorker) return;
     const onControllerChange = () => window.location.reload();
     navigator.serviceWorker.addEventListener('controllerchange', onControllerChange);
     return () => navigator.serviceWorker.removeEventListener('controllerchange', onControllerChange);
-  }, []);
+  }, [inElectron]);
 
   return null;
 }