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/json5/lib/util.js

@@ -0,0 +1,35 @@
+const unicode = require('../lib/unicode')
+
+module.exports = {
+    isSpaceSeparator (c) {
+        return typeof c === 'string' && unicode.Space_Separator.test(c)
+    },
+
+    isIdStartChar (c) {
+        return typeof c === 'string' && (
+            (c >= 'a' && c <= 'z') ||
+        (c >= 'A' && c <= 'Z') ||
+        (c === '$') || (c === '_') ||
+        unicode.ID_Start.test(c)
+        )
+    },
+
+    isIdContinueChar (c) {
+        return typeof c === 'string' && (
+            (c >= 'a' && c <= 'z') ||
+        (c >= 'A' && c <= 'Z') ||
+        (c >= '0' && c <= '9') ||
+        (c === '$') || (c === '_') ||
+        (c === '\u200C') || (c === '\u200D') ||
+        unicode.ID_Continue.test(c)
+        )
+    },
+
+    isDigit (c) {
+        return typeof c === 'string' && /[0-9]/.test(c)
+    },
+
+    isHexDigit (c) {
+        return typeof c === 'string' && /[0-9A-Fa-f]/.test(c)
+    },
+}