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/SetFunctionLength.js

@@ -0,0 +1,28 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+
+var DefinePropertyOrThrow = require('./DefinePropertyOrThrow');
+var HasOwnProperty = require('./HasOwnProperty');
+var IsExtensible = require('./IsExtensible');
+
+// https://262.ecma-international.org/12.0/#sec-setfunctionlength
+
+module.exports = function SetFunctionLength(F, length) {
+	if (typeof F !== 'function' || !IsExtensible(F) || HasOwnProperty(F, 'length')) {
+		throw new $TypeError('Assertion failed: `F` must be an extensible function and lack an own `length` property');
+	}
+	if (typeof length !== 'number') {
+		throw new $TypeError('Assertion failed: `length` must be a Number');
+	}
+	if (length !== Infinity && (!isInteger(length) || length < 0)) {
+		throw new $TypeError('Assertion failed: `length` must be ∞, or an integer >= 0');
+	}
+	return DefinePropertyOrThrow(F, 'length', {
+		'[[Configurable]]': true,
+		'[[Enumerable]]': false,
+		'[[Value]]': length,
+		'[[Writable]]': false
+	});
+};