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/_baseToNumber.js

@@ -0,0 +1,24 @@
+var isSymbol = require('./isSymbol');
+
+/** Used as references for various `Number` constants. */
+var NAN = 0 / 0;
+
+/**
+ * The base implementation of `_.toNumber` which doesn't ensure correct
+ * conversions of binary, hexadecimal, or octal string values.
+ *
+ * @private
+ * @param {*} value The value to process.
+ * @returns {number} Returns the number.
+ */
+function baseToNumber(value) {
+  if (typeof value == 'number') {
+    return value;
+  }
+  if (isSymbol(value)) {
+    return NAN;
+  }
+  return +value;
+}
+
+module.exports = baseToNumber;