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/2021/IntegerIndexedElementSet.js

@@ -0,0 +1,44 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var IsValidIntegerIndex = require('./IsValidIntegerIndex');
+var SetValueInBuffer = require('./SetValueInBuffer');
+var ToBigInt = require('./ToBigInt');
+var ToNumber = require('./ToNumber');
+
+var typedArrayBuffer = require('typed-array-buffer');
+var typedArrayByteOffset = require('typed-array-byte-offset');
+var whichTypedArray = require('which-typed-array');
+
+var tableTAO = require('./tables/typed-array-objects');
+
+// https://262.ecma-international.org/12.0/#sec-integerindexedelementset
+
+module.exports = function IntegerIndexedElementSet(O, index, value) {
+	if (typeof index !== 'number') {
+		throw new $TypeError('Assertion failed: `index` must be a Number');
+	}
+
+	var arrayTypeName = whichTypedArray(O); // step 4.b
+	if (!arrayTypeName) {
+		throw new $TypeError('Assertion failed: `O` must be a TypedArray'); // step 1
+	}
+
+	var contentType = arrayTypeName === 'BigInt64Array' || arrayTypeName === 'BigUint64Array' ? 'BigInt' : 'Number';
+	var numValue = contentType === 'BigInt' ? ToBigInt(value) : ToNumber(value); // steps 2 - 3
+
+	if (IsValidIntegerIndex(O, index)) { // step 4
+		var offset = typedArrayByteOffset(O); // step 4.a
+
+		var elementType = tableTAO.name['$' + arrayTypeName]; // step 4.e
+
+		var elementSize = tableTAO.size['$' + elementType]; // step 4.c
+
+		var indexedPosition = (index * elementSize) + offset; // step 4.d
+
+		SetValueInBuffer(typedArrayBuffer(O), indexedPosition, elementType, numValue, true, 'Unordered'); // step 4.e
+	}
+
+	// 5. Return NormalCompletion(undefined)
+};