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/bytesAsFloat16.js

@@ -0,0 +1,47 @@
+'use strict';
+
+var $pow = require('math-intrinsics/pow');
+
+module.exports = function bytesAsFloat32(rawBytes) {
+	// return new $Float16Array(new $Uint8Array(rawBytes).buffer)[0];
+	/*
+        Let value be the byte elements of rawBytes concatenated and interpreted as a little-endian bit string encoding of an IEEE 754-2019 binary16 value.
+        If value is a NaN, return NaN.
+        Return the Number value that corresponds to value.
+    */
+
+	var bits = (rawBytes[1] << 8) | rawBytes[0];
+
+	// extract sign, exponent, mantissa
+	var sign = bits & 0x8000 ? -1 : 1;
+	var exponent = (bits & 0x7C00) >> 10;
+	var mantissa = bits & 0x03FF;
+
+	// zero (±0)
+	if (exponent === 0 && mantissa === 0) {
+		return sign === 1 ? 0 : -0;
+	}
+
+	// infinities
+	if (exponent === 0x1F && mantissa === 0) {
+		return sign === 1 ? Infinity : -Infinity;
+	}
+
+	// NaN
+	if (exponent === 0x1F && mantissa !== 0) {
+		return NaN;
+	}
+
+	// remove bias (15)
+	exponent -= 15;
+
+	// subnormals
+	if (exponent === -15) {
+		// value = sign * (mantissa) * 2^(1-bias-10) = mantissa * 2^(-14-10)
+		return sign * mantissa * $pow(2, -24);
+	}
+
+	// normals
+	// value = sign * (1 + mantissa/2^10) * 2^exponent
+	return sign * (1 + (mantissa * $pow(2, -10))) * $pow(2, exponent);
+};