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/2024/CloneArrayBuffer.js

@@ -0,0 +1,46 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var GetPrototypeFromConstructor = require('./GetPrototypeFromConstructor');
+var IsConstructor = require('./IsConstructor');
+var IsDetachedBuffer = require('./IsDetachedBuffer');
+var OrdinarySetPrototypeOf = require('./OrdinarySetPrototypeOf');
+
+var isInteger = require('math-intrinsics/isInteger');
+var isArrayBuffer = require('is-array-buffer');
+var arrayBufferSlice = require('arraybuffer.prototype.slice');
+
+// https://262.ecma-international.org/12.0/#sec-clonearraybuffer
+
+module.exports = function CloneArrayBuffer(srcBuffer, srcByteOffset, srcLength, cloneConstructor) {
+	if (!isArrayBuffer(srcBuffer)) {
+		throw new $TypeError('Assertion failed: `srcBuffer` must be an ArrayBuffer instance');
+	}
+	if (!isInteger(srcByteOffset) || srcByteOffset < 0) {
+		throw new $TypeError('Assertion failed: `srcByteOffset` must be a non-negative integer');
+	}
+	if (!isInteger(srcLength) || srcLength < 0) {
+		throw new $TypeError('Assertion failed: `srcLength` must be a non-negative integer');
+	}
+	if (!IsConstructor(cloneConstructor)) {
+		throw new $TypeError('Assertion failed: `cloneConstructor` must be a constructor');
+	}
+
+	// 3. Let targetBuffer be ? AllocateArrayBuffer(cloneConstructor, srcLength).
+	var proto = GetPrototypeFromConstructor(cloneConstructor, '%ArrayBufferPrototype%'); // step 3, kinda
+
+	if (IsDetachedBuffer(srcBuffer)) {
+		throw new $TypeError('`srcBuffer` must not be a detached ArrayBuffer'); // step 4
+	}
+
+	/*
+    5. Let srcBlock be srcBuffer.[[ArrayBufferData]].
+    6. Let targetBlock be targetBuffer.[[ArrayBufferData]].
+    7. Perform CopyDataBlockBytes(targetBlock, 0, srcBlock, srcByteOffset, srcLength).
+    */
+	var targetBuffer = arrayBufferSlice(srcBuffer, srcByteOffset, srcByteOffset + srcLength); // steps 5-7
+	OrdinarySetPrototypeOf(targetBuffer, proto); // step 3
+
+	return targetBuffer; // step 8
+};