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/2023/WordCharacters.js

@@ -0,0 +1,47 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var callBound = require('call-bound');
+var $indexOf = callBound('String.prototype.indexOf');
+
+var Canonicalize = require('./Canonicalize');
+
+var caseFolding = require('../helpers/caseFolding.json');
+var forEach = require('../helpers/forEach');
+var isRegExpRecord = require('../helpers/records/regexp-record');
+var OwnPropertyKeys = require('own-keys');
+
+var basicWordChars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'; // step 1
+
+// https://262.ecma-international.org/14.0/#sec-runtime-semantics-wordcharacters-abstract-operation
+
+module.exports = function WordCharacters(rer) {
+	if (!isRegExpRecord(rer)) {
+		throw new $TypeError('Assertion failed: `rer` must be a RegExp Record');
+	}
+
+	var extraWordChars = '';
+	forEach(OwnPropertyKeys(caseFolding.C), function (c) {
+		if (
+			$indexOf(basicWordChars, c) === -1 // c not in A
+			&& $indexOf(basicWordChars, Canonicalize(rer, c)) > -1 // canonicalized c IS in A
+		) {
+			extraWordChars += caseFolding.C[c]; // step 3
+		}
+	});
+	forEach(OwnPropertyKeys(caseFolding.S), function (c) {
+		if (
+			$indexOf(basicWordChars, c) === -1 // c not in A
+			&& $indexOf(basicWordChars, Canonicalize(rer, c)) > -1 // canonicalized c IS in A
+		) {
+			extraWordChars += caseFolding.S[c]; // step 3
+		}
+	});
+
+	if ((!rer['[[Unicode]]'] || !rer['[[IgnoreCase]]']) && extraWordChars.length > 0) {
+		throw new $TypeError('Assertion failed: `extraWordChars` must be empty when `rer.[[IgnoreCase]]` and `rer.[[Unicode]]` are not both true'); // step 3
+	}
+
+	return basicWordChars + extraWordChars; // step 4
+};