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/2015/IsWordChar.js

@@ -0,0 +1,37 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var IsArray = require('./IsArray');
+var IsInteger = require('./IsInteger');
+
+var every = require('../helpers/every');
+var regexTester = require('safe-regex-test');
+
+var isChar = function isChar(c) {
+	return typeof c === 'string' && c.length === 1;
+};
+
+var isWordCharacter = regexTester(/^[a-zA-Z0-9_]$/);
+
+// https://262.ecma-international.org/6.0/#sec-runtime-semantics-iswordchar-abstract-operation
+
+// note: prior to ES2023, this AO erroneously omitted the latter of its arguments.
+module.exports = function IsWordChar(e, InputLength, Input) {
+	if (!IsInteger(e)) {
+		throw new $TypeError('Assertion failed: `e` must be an integer');
+	}
+	if (!IsInteger(InputLength)) {
+		throw new $TypeError('Assertion failed: `InputLength` must be an integer');
+	}
+	if (!IsArray(Input) || !every(Input, isChar)) {
+		throw new $TypeError('Assertion failed: `Input` must be a List of characters');
+	}
+	if (e === -1 || e === InputLength) {
+		return false; // step 1
+	}
+
+	var c = Input[e]; // step 2
+
+	return isWordCharacter(c); // steps 3-4
+};