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/leaflet.offline/README.md

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+# leaflet.offline
+
+[![npm version](https://badge.fury.io/js/leaflet.offline.svg)](https://badge.fury.io/js/leaflet.offline)
+[![codecov](https://codecov.io/github/allartk/leaflet.offline/graph/badge.svg?token=dy1uNlSvsh)](https://codecov.io/github/allartk/leaflet.offline)
+[![Build Status](https://travis-ci.org/allartk/leaflet.offline.png?branch=master)](https://travis-ci.org/allartk/leaflet.offline)
+
+This library can be used to create maps, which are still available when you are offline and are fast when your connection is not. It works in the browser or can be used in an mobile app based on html and in progressive webapps.
+
+- [examples](https://github.com/allartk/leaflet.offline/tree/main/examples)
+
+## Dependencies
+
+- [Leafletjs](http://leafletjs.com/)
+- [idb](https://www.npmjs.com/package/idb) To store the tiles with promises
+
+## Install
+
+### With npm
+
+The package and it's dependencies can also be downloaded into
+your existing project with [npm](http://npmjs.com):
+
+```
+npm install leaflet.offline
+```
+
+In your script add:
+
+```
+import 'leaflet.offline'
+```
+
+### Manual
+
+Unpack the file for the release (find them under the releasestab ) and add dist/bundle.js in a script tag
+to your page (after leaflet and idb).
+
+### Development
+
+For running the example locally, you'll need to clone the project and run:
+
+```
+npm i && npm run build
+cd docs
+npm install && npm run start
+```
+
+**pull requests welcome**
+
+* You MUST test your code with `npm test` and  `npm run lint`. On wsl wit ubuntu 24.04, install first libasound, libnss3: `sudo apt install libasound2t64 libnss3`, see [puppeteer docs](https://pptr.dev/guides/system-requirements)
+* Please one feature at a time, if you can split your PR, please do so.
+* Also, do not mix a feature with package updates.
+* [Use commit message conventions](https://github.com/conventional-changelog/commitlint/tree/master/%40commitlint/config-conventional#rules)
+
+## Api
+
+Generate docs with
+
+```
+npm run-script docs
+```