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/lodash/uniqueId.js

@@ -0,0 +1,28 @@
+var toString = require('./toString');
+
+/** Used to generate unique IDs. */
+var idCounter = 0;
+
+/**
+ * Generates a unique ID. If `prefix` is given, the ID is appended to it.
+ *
+ * @static
+ * @since 0.1.0
+ * @memberOf _
+ * @category Util
+ * @param {string} [prefix=''] The value to prefix the ID with.
+ * @returns {string} Returns the unique ID.
+ * @example
+ *
+ * _.uniqueId('contact_');
+ * // => 'contact_104'
+ *
+ * _.uniqueId();
+ * // => '105'
+ */
+function uniqueId(prefix) {
+  var id = ++idCounter;
+  return toString(prefix) + id;
+}
+
+module.exports = uniqueId;