Fix PWA to open as standalone app instead of browser tab

## manifest.json
- Add `id` and `scope` fields for proper PWA identification
- Split icon purposes into separate entries (was "any maskable", now separate)
- Add `prefer_related_applications: false`

## index.html
- Add `viewport-fit=cover` for notched devices
- Add `mobile-web-app-capable` meta tag
- Add `application-name` and `msapplication` meta tags
- Add both 192px and 512px apple-touch-icon sizes

## styles.css
- Add safe-area-inset padding for notched devices (iPhone X+)
- Use 100dvh for proper mobile viewport height
- Add bottom safe area to toast container and macro grid

## service-worker.js
- Bump cache version to v2 to force update

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

web/service-worker.js

@@ -1,5 +1,5 @@
 // MacroPad PWA Service Worker
-const CACHE_NAME = 'macropad-v1';
+const CACHE_NAME = 'macropad-v2';
 const ASSETS_TO_CACHE = [
     '/',
     '/static/css/styles.css',