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/tempy/index.js

@@ -0,0 +1,56 @@
+'use strict';
+const fs = require('fs');
+const path = require('path');
+const uniqueString = require('unique-string');
+const tempDir = require('temp-dir');
+const isStream = require('is-stream');
+const stream = require('stream');
+const {promisify} = require('util');
+
+const pipeline = promisify(stream.pipeline);
+const {writeFile} = fs.promises;
+
+const getPath = (prefix = '') => path.join(tempDir, prefix + uniqueString());
+
+const writeStream = async (filePath, data) => pipeline(data, fs.createWriteStream(filePath));
+
+module.exports.file = options => {
+	options = {
+		...options
+	};
+
+	if (options.name) {
+		if (options.extension !== undefined && options.extension !== null) {
+			throw new Error('The `name` and `extension` options are mutually exclusive');
+		}
+
+		return path.join(module.exports.directory(), options.name);
+	}
+
+	return getPath() + (options.extension === undefined || options.extension === null ? '' : '.' + options.extension.replace(/^\./, ''));
+};
+
+module.exports.directory = ({prefix = ''} = {}) => {
+	const directory = getPath(prefix);
+	fs.mkdirSync(directory);
+	return directory;
+};
+
+module.exports.write = async (data, options) => {
+	const filename = module.exports.file(options);
+	const write = isStream(data) ? writeStream : writeFile;
+	await write(filename, data);
+	return filename;
+};
+
+module.exports.writeSync = (data, options) => {
+	const filename = module.exports.file(options);
+	fs.writeFileSync(filename, data);
+	return filename;
+};
+
+Object.defineProperty(module.exports, 'root', {
+	get() {
+		return tempDir;
+	}
+});