Serve PWA icons from fresh /icons/v2/ URLs with every iOS size

iOS showed a letter tile ('N') when adding to the Home Screen. The live files were fine, but a
reverse proxy in front of the app serves static files with a long cache lifetime (live icon.svg
and sw.js were stale) and iOS remembers a failed icon per URL.

- New versioned URLs no proxy/phone has cached; old paths kept for existing installs
- apple-touch-icon declared at 180/167/152/120 (opaque 8-bit RGB PNGs) for app and dashboard
- 180px icon also listed in both manifests; notification icons and root fallbacks use v2
- Service worker cache bumped

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/server.js

@@ -638,7 +638,7 @@ app.use(express.static(path.join(__dirname, 'public')));
 
 // Prevent browser favicon requests from showing noisy 404s.
 // Icons iOS and browsers request from the site root when a page doesn't declare one
-const ICON_DIR = path.join(__dirname, 'public', 'icons');
+const ICON_DIR = path.join(__dirname, 'public', 'icons', 'v2');
 app.get(['/apple-touch-icon.png', '/apple-touch-icon-precomposed.png'], (_req, res) => res.sendFile(path.join(ICON_DIR, 'apple-touch-icon.png')));
 app.get('/favicon.ico', (_req, res) => res.sendFile(path.join(ICON_DIR, 'icon-192.png')));