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/es-abstract/2025/ToNumber.js

@@ -0,0 +1,26 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $TypeError = require('es-errors/type');
+var $Number = GetIntrinsic('%Number%');
+var isPrimitive = require('../helpers/isPrimitive');
+
+var ToPrimitive = require('./ToPrimitive');
+var StringToNumber = require('./StringToNumber');
+
+// https://262.ecma-international.org/13.0/#sec-tonumber
+
+module.exports = function ToNumber(argument) {
+	var value = isPrimitive(argument) ? argument : ToPrimitive(argument, $Number);
+	if (typeof value === 'symbol') {
+		throw new $TypeError('Cannot convert a Symbol value to a number');
+	}
+	if (typeof value === 'bigint') {
+		throw new $TypeError('Conversion from \'BigInt\' to \'number\' is not allowed.');
+	}
+	if (typeof value === 'string') {
+		return StringToNumber(value);
+	}
+	return +value;
+};