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/workbox-build/build/lib/get-source-map-url.js

@@ -0,0 +1,32 @@
+"use strict";
+/*
+  Copyright 2022 Google LLC
+
+  Use of this source code is governed by an MIT-style
+  license that can be found in the LICENSE file or at
+  https://opensource.org/licenses/MIT.
+*/
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.getSourceMapURL = void 0;
+// Adapted from https://github.com/lydell/source-map-url/blob/master/source-map-url.js
+// See https://github.com/GoogleChrome/workbox/issues/3019
+const innerRegex = /[#@] sourceMappingURL=([^\s'"]*)/;
+const regex = RegExp('(?:' +
+    '/\\*' +
+    '(?:\\s*\r?\n(?://)?)?' +
+    '(?:' +
+    innerRegex.source +
+    ')' +
+    '\\s*' +
+    '\\*/' +
+    '|' +
+    '//(?:' +
+    innerRegex.source +
+    ')' +
+    ')' +
+    '\\s*');
+function getSourceMapURL(srcContents) {
+    const match = srcContents.match(regex);
+    return match ? match[1] || match[2] || '' : null;
+}
+exports.getSourceMapURL = getSourceMapURL;