Add progressive web app companion for cross-platform access

Vite + TypeScript PWA that mirrors the Android app's core features:
- Pre-processed shelter data (build-time UTM33N→WGS84 conversion)
- Leaflet map with shelter markers, user location, and offline tiles
- Canvas compass arrow (ported from DirectionArrowView.kt)
- IndexedDB shelter cache with 7-day staleness check
- Service worker with CacheFirst tiles and precached app shell
- i18n for en, nb, nn (ported from Android strings.xml)
- iOS/Android compass handling with low-pass filter
- Respects user map interaction (no auto-snap on pan/zoom)
- Build revision cache-breaker for reliable SW updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pwa/node_modules/randombytes/README.md

@@ -0,0 +1,14 @@
+randombytes
+===
+
+[![Version](http://img.shields.io/npm/v/randombytes.svg)](https://www.npmjs.org/package/randombytes) [![Build Status](https://travis-ci.org/crypto-browserify/randombytes.svg?branch=master)](https://travis-ci.org/crypto-browserify/randombytes)
+
+randombytes from node that works in the browser.  In node you just get crypto.randomBytes, but in the browser it uses .crypto/msCrypto.getRandomValues
+
+```js
+var randomBytes = require('randombytes');
+randomBytes(16);//get 16 random bytes
+randomBytes(16, function (err, resp) {
+  // resp is 16 random bytes
+});
+```