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/_baseMerge.js

@@ -0,0 +1,42 @@
+var Stack = require('./_Stack'),
+    assignMergeValue = require('./_assignMergeValue'),
+    baseFor = require('./_baseFor'),
+    baseMergeDeep = require('./_baseMergeDeep'),
+    isObject = require('./isObject'),
+    keysIn = require('./keysIn'),
+    safeGet = require('./_safeGet');
+
+/**
+ * The base implementation of `_.merge` without support for multiple sources.
+ *
+ * @private
+ * @param {Object} object The destination object.
+ * @param {Object} source The source object.
+ * @param {number} srcIndex The index of `source`.
+ * @param {Function} [customizer] The function to customize merged values.
+ * @param {Object} [stack] Tracks traversed source values and their merged
+ *  counterparts.
+ */
+function baseMerge(object, source, srcIndex, customizer, stack) {
+  if (object === source) {
+    return;
+  }
+  baseFor(source, function(srcValue, key) {
+    stack || (stack = new Stack);
+    if (isObject(srcValue)) {
+      baseMergeDeep(object, source, key, srcIndex, baseMerge, customizer, stack);
+    }
+    else {
+      var newValue = customizer
+        ? customizer(safeGet(object, key), srcValue, (key + ''), object, source, stack)
+        : undefined;
+
+      if (newValue === undefined) {
+        newValue = srcValue;
+      }
+      assignMergeValue(object, key, newValue);
+    }
+  }, keysIn);
+}
+
+module.exports = baseMerge;