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/2025/Number/remainder.js

@@ -0,0 +1,38 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+var isNaN = require('math-intrinsics/isNaN');
+var isFinite = require('math-intrinsics/isFinite');
+
+var truncate = require('../truncate');
+
+// https://262.ecma-international.org/14.0/#sec-numeric-types-number-remainder
+
+module.exports = function NumberRemainder(n, d) {
+	if (typeof n !== 'number' || typeof d !== 'number') {
+		throw new $TypeError('Assertion failed: `n` and `d` arguments must be Numbers');
+	}
+
+	// If either operand is NaN, the result is NaN.
+	// If the dividend is an infinity, or the divisor is a zero, or both, the result is NaN.
+	if (isNaN(n) || isNaN(d) || !isFinite(n) || d === 0) {
+		return NaN;
+	}
+
+	// If the dividend is finite and the divisor is an infinity, the result equals the dividend.
+	// If the dividend is a zero and the divisor is nonzero and finite, the result is the same as the dividend.
+	if (!isFinite(d) || n === 0) {
+		return n;
+	}
+
+	if (!isFinite(n) || !isFinite(d) || n === 0 || d === 0) {
+		throw new $TypeError('Assertion failed: `n` and `d` arguments must be finite and nonzero');
+	}
+	var quotient = n / d;
+	var q = truncate(quotient);
+	var r = n - (d * q);
+	if (r === 0 && n < 0) {
+		return -0;
+	}
+	return r;
+};