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/GetNamedTimeZoneEpochNanoseconds.js

@@ -0,0 +1,72 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var GetUTCEpochNanoseconds = require('./GetUTCEpochNanoseconds');
+
+var isInteger = require('math-intrinsics/isInteger');
+
+// https://262.ecma-international.org/14.0/#sec-getnamedtimezoneepochnanoseconds
+
+// eslint-disable-next-line max-params
+module.exports = function GetNamedTimeZoneEpochNanoseconds(
+	timeZoneIdentifier,
+	year,
+	month,
+	day,
+	hour,
+	minute,
+	second,
+	millisecond,
+	microsecond,
+	nanosecond
+) {
+	if (typeof timeZoneIdentifier !== 'string') {
+		throw new $TypeError('Assertion failed: `timeZoneIdentifier` must be a string');
+	}
+	if (!isInteger(year)) {
+		throw new $TypeError('Assertion failed: `year` must be an integral number');
+	}
+	if (!isInteger(month) || month < 1 || month > 12) {
+		throw new $TypeError('Assertion failed: `month` must be an integral number between 1 and 12, inclusive');
+	}
+	if (!isInteger(day) || day < 1 || day > 31) {
+		throw new $TypeError('Assertion failed: `day` must be an integral number between 1 and 31, inclusive');
+	}
+	if (!isInteger(hour) || hour < 0 || hour > 23) {
+		throw new $TypeError('Assertion failed: `hour` must be an integral number between 0 and 23, inclusive');
+	}
+	if (!isInteger(minute) || minute < 0 || minute > 59) {
+		throw new $TypeError('Assertion failed: `minute` must be an integral number between 0 and 59, inclusive');
+	}
+	if (!isInteger(second) || second < 0 || second > 999) {
+		throw new $TypeError('Assertion failed: `second` must be an integral number between 0 and 999, inclusive');
+	}
+	if (!isInteger(millisecond) || millisecond < 0 || millisecond > 999) {
+		throw new $TypeError('Assertion failed: `millisecond` must be an integral number between 0 and 999, inclusive');
+	}
+	if (!isInteger(microsecond) || microsecond < 0 || microsecond > 999) {
+		throw new $TypeError('Assertion failed: `microsecond` must be an integral number between 0 and 999, inclusive');
+	}
+	if (!isInteger(nanosecond) || nanosecond < 0 || nanosecond > 999) {
+		throw new $TypeError('Assertion failed: `nanosecond` must be an integral number between 0 and 999, inclusive');
+	}
+
+	if (timeZoneIdentifier !== 'UTC') {
+		throw new $TypeError('Assertion failed: only UTC time zone is supported'); // step 1
+	}
+
+	var epochNanoseconds = GetUTCEpochNanoseconds(
+		year,
+		month,
+		day,
+		hour,
+		minute,
+		second,
+		millisecond,
+		microsecond,
+		nanosecond
+	); // step 2
+
+	return [epochNanoseconds]; // step 3
+};