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/isDate.js

@@ -0,0 +1,27 @@
+var baseIsDate = require('./_baseIsDate'),
+    baseUnary = require('./_baseUnary'),
+    nodeUtil = require('./_nodeUtil');
+
+/* Node.js helper references. */
+var nodeIsDate = nodeUtil && nodeUtil.isDate;
+
+/**
+ * Checks if `value` is classified as a `Date` object.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a date object, else `false`.
+ * @example
+ *
+ * _.isDate(new Date);
+ * // => true
+ *
+ * _.isDate('Mon April 23 2012');
+ * // => false
+ */
+var isDate = nodeIsDate ? baseUnary(nodeIsDate) : baseIsDate;
+
+module.exports = isDate;