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-broadcast-update/responsesAreSame.js

@@ -0,0 +1,47 @@
+/*
+  Copyright 2018 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 { WorkboxError } from 'workbox-core/_private/WorkboxError.js';
+import { logger } from 'workbox-core/_private/logger.js';
+import './_version.js';
+/**
+ * Given two `Response's`, compares several header values to see if they are
+ * the same or not.
+ *
+ * @param {Response} firstResponse
+ * @param {Response} secondResponse
+ * @param {Array<string>} headersToCheck
+ * @return {boolean}
+ *
+ * @memberof workbox-broadcast-update
+ */
+const responsesAreSame = (firstResponse, secondResponse, headersToCheck) => {
+    if (process.env.NODE_ENV !== 'production') {
+        if (!(firstResponse instanceof Response && secondResponse instanceof Response)) {
+            throw new WorkboxError('invalid-responses-are-same-args');
+        }
+    }
+    const atLeastOneHeaderAvailable = headersToCheck.some((header) => {
+        return (firstResponse.headers.has(header) && secondResponse.headers.has(header));
+    });
+    if (!atLeastOneHeaderAvailable) {
+        if (process.env.NODE_ENV !== 'production') {
+            logger.warn(`Unable to determine where the response has been updated ` +
+                `because none of the headers that would be checked are present.`);
+            logger.debug(`Attempting to compare the following: `, firstResponse, secondResponse, headersToCheck);
+        }
+        // Just return true, indicating the that responses are the same, since we
+        // can't determine otherwise.
+        return true;
+    }
+    return headersToCheck.every((header) => {
+        const headerStateComparison = firstResponse.headers.has(header) === secondResponse.headers.has(header);
+        const headerValueComparison = firstResponse.headers.get(header) === secondResponse.headers.get(header);
+        return headerStateComparison && headerValueComparison;
+    });
+};
+export { responsesAreSame };