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/is-string/README.md

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+# is-string <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
+
+[![github actions][actions-image]][actions-url]
+[![coverage][codecov-image]][codecov-url]
+[![dependency status][deps-svg]][deps-url]
+[![dev dependency status][dev-deps-svg]][dev-deps-url]
+[![License][license-image]][license-url]
+[![Downloads][downloads-image]][downloads-url]
+
+[![npm badge][npm-badge-png]][package-url]
+
+Is this value a JS String object or primitive? This module works cross-realm/iframe, and despite ES6 @@toStringTag.
+
+## Example
+
+```js
+var isString = require('is-string');
+var assert = require('assert');
+
+assert.notOk(isString(undefined));
+assert.notOk(isString(null));
+assert.notOk(isString(false));
+assert.notOk(isString(true));
+assert.notOk(isString(function () {}));
+assert.notOk(isString([]));
+assert.notOk(isString({}));
+assert.notOk(isString(/a/g));
+assert.notOk(isString(new RegExp('a', 'g')));
+assert.notOk(isString(new Date()));
+assert.notOk(isString(42));
+assert.notOk(isString(NaN));
+assert.notOk(isString(Infinity));
+assert.notOk(isString(new Number(42)));
+
+assert.ok(isString('foo'));
+assert.ok(isString(Object('foo')));
+```
+
+## Tests
+Simply clone the repo, `npm install`, and run `npm test`
+
+[package-url]: https://npmjs.org/package/is-string
+[npm-version-svg]: https://versionbadg.es/inspect-js/is-string.svg
+[deps-svg]: https://david-dm.org/inspect-js/is-string.svg
+[deps-url]: https://david-dm.org/inspect-js/is-string
+[dev-deps-svg]: https://david-dm.org/inspect-js/is-string/dev-status.svg
+[dev-deps-url]: https://david-dm.org/inspect-js/is-string#info=devDependencies
+[npm-badge-png]: https://nodei.co/npm/is-string.png?downloads=true&stars=true
+[license-image]: https://img.shields.io/npm/l/is-string.svg
+[license-url]: LICENSE
+[downloads-image]: https://img.shields.io/npm/dm/is-string.svg
+[downloads-url]: https://npm-stat.com/charts.html?package=is-string
+[codecov-image]: https://codecov.io/gh/inspect-js/is-string/branch/main/graphs/badge.svg
+[codecov-url]: https://app.codecov.io/gh/inspect-js/is-string/
+[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/inspect-js/is-string
+[actions-url]: https://github.com/inspect-js/is-string/actions