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/require-from-string/index.js

@@ -0,0 +1,34 @@
+'use strict';
+
+var Module = require('module');
+var path = require('path');
+
+module.exports = function requireFromString(code, filename, opts) {
+	if (typeof filename === 'object') {
+		opts = filename;
+		filename = undefined;
+	}
+
+	opts = opts || {};
+	filename = filename || '';
+
+	opts.appendPaths = opts.appendPaths || [];
+	opts.prependPaths = opts.prependPaths || [];
+
+	if (typeof code !== 'string') {
+		throw new Error('code must be a string, not ' + typeof code);
+	}
+
+	var paths = Module._nodeModulePaths(path.dirname(filename));
+
+	var parent = module.parent;
+	var m = new Module(filename, parent);
+	m.filename = filename;
+	m.paths = [].concat(opts.prependPaths).concat(paths).concat(opts.appendPaths);
+	m._compile(code, filename);
+
+	var exports = m.exports;
+	parent && parent.children && parent.children.splice(parent.children.indexOf(m), 1);
+
+	return exports;
+};