feat: Add iOS push notification support (iOS 16.4+)

- Platform detection utilities (is_ios, is_standalone, supports_push)
- iOS-specific meta tags and Apple touch icons
- Auto-detect iOS and show user-friendly message when not in standalone mode
- Enhanced Service Worker with iOS-compatible notification options
- Comprehensive iOS push notification documentation
- manifest.json scope for PWA compliance
- Only works when added to Home Screen (iOS Safari limitation)

frontend/index.html

@@ -11,9 +11,13 @@
         <!-- PWA & Mobile Capable -->
         <meta name="mobile-web-app-capable" content="yes" />
         <meta name="apple-mobile-web-app-capable" content="yes" />
+        <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
+        <meta name="apple-mobile-web-app-title" content="VibeTorrent" />
         <meta name="theme-color" content="#111827" />
         <link rel="manifest" href="manifest.json" />
         <link rel="apple-touch-icon" href="icon-192.png" />
+        <link rel="apple-touch-icon" sizes="192x192" href="icon-192.png" />
+        <link rel="apple-touch-icon" sizes="512x512" href="icon-512.png" />
 
         <!-- Trunk Assets -->
         <link data-trunk rel="rust" href="Cargo.toml" data-wasm-opt="0" />