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/isPlainObject.js

@@ -0,0 +1,62 @@
+var baseGetTag = require('./_baseGetTag'),
+    getPrototype = require('./_getPrototype'),
+    isObjectLike = require('./isObjectLike');
+
+/** `Object#toString` result references. */
+var objectTag = '[object Object]';
+
+/** Used for built-in method references. */
+var funcProto = Function.prototype,
+    objectProto = Object.prototype;
+
+/** Used to resolve the decompiled source of functions. */
+var funcToString = funcProto.toString;
+
+/** Used to check objects for own properties. */
+var hasOwnProperty = objectProto.hasOwnProperty;
+
+/** Used to infer the `Object` constructor. */
+var objectCtorString = funcToString.call(Object);
+
+/**
+ * Checks if `value` is a plain object, that is, an object created by the
+ * `Object` constructor or one with a `[[Prototype]]` of `null`.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.8.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a plain object, else `false`.
+ * @example
+ *
+ * function Foo() {
+ *   this.a = 1;
+ * }
+ *
+ * _.isPlainObject(new Foo);
+ * // => false
+ *
+ * _.isPlainObject([1, 2, 3]);
+ * // => false
+ *
+ * _.isPlainObject({ 'x': 0, 'y': 0 });
+ * // => true
+ *
+ * _.isPlainObject(Object.create(null));
+ * // => true
+ */
+function isPlainObject(value) {
+  if (!isObjectLike(value) || baseGetTag(value) != objectTag) {
+    return false;
+  }
+  var proto = getPrototype(value);
+  if (proto === null) {
+    return true;
+  }
+  var Ctor = hasOwnProperty.call(proto, 'constructor') && proto.constructor;
+  return typeof Ctor == 'function' && Ctor instanceof Ctor &&
+    funcToString.call(Ctor) == objectCtorString;
+}
+
+module.exports = isPlainObject;