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/leven/readme.md

@@ -0,0 +1,50 @@
+# leven [![Build Status](https://travis-ci.org/sindresorhus/leven.svg?branch=master)](https://travis-ci.org/sindresorhus/leven)
+
+> Measure the difference between two strings<br>
+> One of the fastest JS implementations of the [Levenshtein distance](https://en.wikipedia.org/wiki/Levenshtein_distance) algorithm
+
+
+## Install
+
+```
+$ npm install leven
+```
+
+
+## Usage
+
+```js
+const leven = require('leven');
+
+leven('cat', 'cow');
+//=> 2
+```
+
+
+## Benchmark
+
+```
+$ npm run bench
+```
+
+```
+         165,926 op/s » leven
+         164,398 op/s » talisman
+           1,044 op/s » levenshtein-edit-distance
+             628 op/s » fast-levenshtein
+             497 op/s » levenshtein-component
+             195 op/s » ld
+             190 op/s » levenshtein
+             168 op/s » levdist
+              10 op/s » natural
+```
+
+
+## Related
+
+- [leven-cli](https://github.com/sindresorhus/leven-cli) - CLI for this module
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)