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/2016/Canonicalize.js

@@ -0,0 +1,51 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var callBound = require('call-bound');
+var hasOwn = require('hasown');
+
+var $charCodeAt = callBound('String.prototype.charCodeAt');
+var $toUpperCase = callBound('String.prototype.toUpperCase');
+
+var caseFolding = require('../helpers/caseFolding.json');
+
+// https://262.ecma-international.org/6.0/#sec-runtime-semantics-canonicalize-ch
+
+module.exports = function Canonicalize(ch, IgnoreCase, Unicode) {
+	if (typeof ch !== 'string') {
+		throw new $TypeError('Assertion failed: `ch` must be a character');
+	}
+
+	if (typeof IgnoreCase !== 'boolean' || typeof Unicode !== 'boolean') {
+		throw new $TypeError('Assertion failed: `IgnoreCase` and `Unicode` must be Booleans');
+	}
+
+	if (!IgnoreCase) {
+		return ch; // step 1
+	}
+
+	if (Unicode) { // step 2
+		if (hasOwn(caseFolding.C, ch)) {
+			return caseFolding.C[ch];
+		}
+		if (hasOwn(caseFolding.S, ch)) {
+			return caseFolding.S[ch];
+		}
+		return ch; // step 2.b
+	}
+
+	var u = $toUpperCase(ch); // step 2
+
+	if (u.length !== 1) {
+		return ch; // step 3
+	}
+
+	var cu = u; // step 4
+
+	if ($charCodeAt(ch, 0) >= 128 && $charCodeAt(cu, 0) < 128) {
+		return ch; // step 5
+	}
+
+	return cu;
+};