Install-as-app guide and iPhone safe-area support

- Install banner (phones), Settings guide and dialog with iPhone/iPad and Android steps,
  native Install button where supported; steps also on the dashboard Account page
- apple-touch-icon now a PNG (iOS ignores SVG icons)
- Shared pwa-safe.css: dark cap behind the status bar/Dynamic Island in the installed app,
  inset-aware offline banner, pull-to-refresh, bottom bars, full-screen map, dialogs
- Landscape-aware content gutters; measured top-bar height; viewport-fit=cover on every page

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

app/public/sw.js

@@ -4,7 +4,7 @@ self.addEventListener('message', event => {
   if (event.data === 'skipWaiting') self.skipWaiting();
 });
 
-const CACHE = 'weather-v9';
+const CACHE = 'weather-v11';
 
 // App shell cached on install for offline resilience.
 const PRECACHE = [
@@ -14,6 +14,7 @@ const PRECACHE = [
   '/station-live.css',
   '/station-live.js',
   '/app-ui.css',
+  '/pwa-safe.css',
   '/app-ui.js',
   '/manifest.json',
   '/icons/icon.svg'