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/helpers/fractionToBinaryString.js

@@ -0,0 +1,33 @@
+'use strict';
+
+var MAX_ITER = 1075; // 1023+52 (subnormals) => BIAS+NUM_SIGNFICAND_BITS-1
+var maxBits = 54; // only 53 bits for fraction
+
+module.exports = function fractionToBitString(x) {
+	var str = '';
+	if (x === 0) {
+		return str;
+	}
+	var j = MAX_ITER;
+
+	var y;
+	// Each time we multiply by 2 and find a ones digit, add a '1'; otherwise, add a '0'..
+	for (var i = 0; i < MAX_ITER; i += 1) {
+		y = x * 2;
+		if (y >= 1) {
+			x = y - 1; // eslint-disable-line no-param-reassign
+			str += '1';
+			if (j === MAX_ITER) {
+				j = i; // first 1
+			}
+		} else {
+			x = y; // eslint-disable-line no-param-reassign
+			str += '0';
+		}
+		// Stop when we have no more decimals to process or in the event we found a fraction which cannot be represented in a finite number of bits...
+		if (y === 1 || i - j > maxBits) {
+			return str;
+		}
+	}
+	return str;
+};