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-precaching/utils/generateURLVariations.js

@@ -0,0 +1,42 @@
+/*
+  Copyright 2019 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.
+*/
+import { removeIgnoredSearchParams } from './removeIgnoredSearchParams.js';
+import '../_version.js';
+/**
+ * Generator function that yields possible variations on the original URL to
+ * check, one at a time.
+ *
+ * @param {string} url
+ * @param {Object} options
+ *
+ * @private
+ * @memberof workbox-precaching
+ */
+export function* generateURLVariations(url, { ignoreURLParametersMatching = [/^utm_/, /^fbclid$/], directoryIndex = 'index.html', cleanURLs = true, urlManipulation, } = {}) {
+    const urlObject = new URL(url, location.href);
+    urlObject.hash = '';
+    yield urlObject.href;
+    const urlWithoutIgnoredParams = removeIgnoredSearchParams(urlObject, ignoreURLParametersMatching);
+    yield urlWithoutIgnoredParams.href;
+    if (directoryIndex && urlWithoutIgnoredParams.pathname.endsWith('/')) {
+        const directoryURL = new URL(urlWithoutIgnoredParams.href);
+        directoryURL.pathname += directoryIndex;
+        yield directoryURL.href;
+    }
+    if (cleanURLs) {
+        const cleanURL = new URL(urlWithoutIgnoredParams.href);
+        cleanURL.pathname += '.html';
+        yield cleanURL.href;
+    }
+    if (urlManipulation) {
+        const additionalURLs = urlManipulation({ url: urlObject });
+        for (const urlToAttempt of additionalURLs) {
+            yield urlToAttempt.href;
+        }
+    }
+}