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/_baseSlice.js

@@ -0,0 +1,31 @@
+/**
+ * The base implementation of `_.slice` without an iteratee call guard.
+ *
+ * @private
+ * @param {Array} array The array to slice.
+ * @param {number} [start=0] The start position.
+ * @param {number} [end=array.length] The end position.
+ * @returns {Array} Returns the slice of `array`.
+ */
+function baseSlice(array, start, end) {
+  var index = -1,
+      length = array.length;
+
+  if (start < 0) {
+    start = -start > length ? 0 : (length + start);
+  }
+  end = end > length ? length : end;
+  if (end < 0) {
+    end += length;
+  }
+  length = start > end ? 0 : ((end - start) >>> 0);
+  start >>>= 0;
+
+  var result = Array(length);
+  while (++index < length) {
+    result[index] = array[index + start];
+  }
+  return result;
+}
+
+module.exports = baseSlice;