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/_escapeStringChar.js

@@ -0,0 +1,22 @@
+/** Used to escape characters for inclusion in compiled string literals. */
+var stringEscapes = {
+  '\\': '\\',
+  "'": "'",
+  '\n': 'n',
+  '\r': 'r',
+  '\u2028': 'u2028',
+  '\u2029': 'u2029'
+};
+
+/**
+ * Used by `_.template` to escape characters for inclusion in compiled string literals.
+ *
+ * @private
+ * @param {string} chr The matched character to escape.
+ * @returns {string} Returns the escaped character.
+ */
+function escapeStringChar(chr) {
+  return '\\' + stringEscapes[chr];
+}
+
+module.exports = escapeStringChar;