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/toSafeInteger.js

@@ -0,0 +1,37 @@
+var baseClamp = require('./_baseClamp'),
+    toInteger = require('./toInteger');
+
+/** Used as references for various `Number` constants. */
+var MAX_SAFE_INTEGER = 9007199254740991;
+
+/**
+ * Converts `value` to a safe integer. A safe integer can be compared and
+ * represented correctly.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.0.0
+ * @category Lang
+ * @param {*} value The value to convert.
+ * @returns {number} Returns the converted integer.
+ * @example
+ *
+ * _.toSafeInteger(3.2);
+ * // => 3
+ *
+ * _.toSafeInteger(Number.MIN_VALUE);
+ * // => 0
+ *
+ * _.toSafeInteger(Infinity);
+ * // => 9007199254740991
+ *
+ * _.toSafeInteger('3.2');
+ * // => 3
+ */
+function toSafeInteger(value) {
+  return value
+    ? baseClamp(toInteger(value), -MAX_SAFE_INTEGER, MAX_SAFE_INTEGER)
+    : (value === 0 ? value : 0);
+}
+
+module.exports = toSafeInteger;