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/set-proto/index.js

@@ -0,0 +1,25 @@
+'use strict';
+
+var reflectSetProto = require('./Reflect.setPrototypeOf');
+var originalSetProto = require('./Object.setPrototypeOf');
+
+var setDunderProto = require('dunder-proto/set');
+
+var $TypeError = require('es-errors/type');
+
+/** @type {import('.')} */
+module.exports = reflectSetProto
+	? function setProto(O, proto) {
+		// @ts-expect-error TS can't narrow inside a closure, for some reason
+		if (reflectSetProto(O, proto)) {
+			return O;
+		}
+		throw new $TypeError('Reflect.setPrototypeOf: failed to set [[Prototype]]');
+	}
+	: originalSetProto || (
+		setDunderProto ? function setProto(O, proto) {
+			// @ts-expect-error TS can't narrow inside a closure, for some reason
+			setDunderProto(O, proto);
+			return O;
+		} : null
+	);