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/is-regex/index.js

@@ -0,0 +1,69 @@
+'use strict';
+
+var callBound = require('call-bound');
+var hasToStringTag = require('has-tostringtag/shams')();
+var hasOwn = require('hasown');
+var gOPD = require('gopd');
+
+/** @type {import('.')} */
+var fn;
+
+if (hasToStringTag) {
+	/** @type {(receiver: ThisParameterType<typeof RegExp.prototype.exec>, ...args: Parameters<typeof RegExp.prototype.exec>) => ReturnType<typeof RegExp.prototype.exec>} */
+	var $exec = callBound('RegExp.prototype.exec');
+	/** @type {object} */
+	var isRegexMarker = {};
+
+	var throwRegexMarker = function () {
+		throw isRegexMarker;
+	};
+	/** @type {{ toString(): never, valueOf(): never, [Symbol.toPrimitive]?(): never }} */
+	var badStringifier = {
+		toString: throwRegexMarker,
+		valueOf: throwRegexMarker
+	};
+
+	if (typeof Symbol.toPrimitive === 'symbol') {
+		badStringifier[Symbol.toPrimitive] = throwRegexMarker;
+	}
+
+	/** @type {import('.')} */
+	// @ts-expect-error TS can't figure out that the $exec call always throws
+	// eslint-disable-next-line consistent-return
+	fn = function isRegex(value) {
+		if (!value || typeof value !== 'object') {
+			return false;
+		}
+
+		// eslint-disable-next-line no-extra-parens
+		var descriptor = /** @type {NonNullable<typeof gOPD>} */ (gOPD)(/** @type {{ lastIndex?: unknown }} */ (value), 'lastIndex');
+		var hasLastIndexDataProperty = descriptor && hasOwn(descriptor, 'value');
+		if (!hasLastIndexDataProperty) {
+			return false;
+		}
+
+		try {
+			// eslint-disable-next-line no-extra-parens
+			$exec(value, /** @type {string} */ (/** @type {unknown} */ (badStringifier)));
+		} catch (e) {
+			return e === isRegexMarker;
+		}
+	};
+} else {
+	/** @type {(receiver: ThisParameterType<typeof Object.prototype.toString>, ...args: Parameters<typeof Object.prototype.toString>) => ReturnType<typeof Object.prototype.toString>} */
+	var $toString = callBound('Object.prototype.toString');
+	/** @const @type {'[object RegExp]'} */
+	var regexClass = '[object RegExp]';
+
+	/** @type {import('.')} */
+	fn = function isRegex(value) {
+		// In older browsers, typeof regex incorrectly returns 'function'
+		if (!value || (typeof value !== 'object' && typeof value !== 'function')) {
+			return false;
+		}
+
+		return $toString(value) === regexClass;
+	};
+}
+
+module.exports = fn;