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-expiration/CacheExpiration.d.ts

@@ -0,0 +1,66 @@
+import './_version.js';
+interface CacheExpirationConfig {
+    maxEntries?: number;
+    maxAgeSeconds?: number;
+    matchOptions?: CacheQueryOptions;
+}
+/**
+ * The `CacheExpiration` class allows you define an expiration and / or
+ * limit on the number of responses stored in a
+ * [`Cache`](https://developer.mozilla.org/en-US/docs/Web/API/Cache).
+ *
+ * @memberof workbox-expiration
+ */
+declare class CacheExpiration {
+    private _isRunning;
+    private _rerunRequested;
+    private readonly _maxEntries?;
+    private readonly _maxAgeSeconds?;
+    private readonly _matchOptions?;
+    private readonly _cacheName;
+    private readonly _timestampModel;
+    /**
+     * To construct a new CacheExpiration instance you must provide at least
+     * one of the `config` properties.
+     *
+     * @param {string} cacheName Name of the cache to apply restrictions to.
+     * @param {Object} config
+     * @param {number} [config.maxEntries] The maximum number of entries to cache.
+     * Entries used the least will be removed as the maximum is reached.
+     * @param {number} [config.maxAgeSeconds] The maximum age of an entry before
+     * it's treated as stale and removed.
+     * @param {Object} [config.matchOptions] The [`CacheQueryOptions`](https://developer.mozilla.org/en-US/docs/Web/API/Cache/delete#Parameters)
+     * that will be used when calling `delete()` on the cache.
+     */
+    constructor(cacheName: string, config?: CacheExpirationConfig);
+    /**
+     * Expires entries for the given cache and given criteria.
+     */
+    expireEntries(): Promise<void>;
+    /**
+     * Update the timestamp for the given URL. This ensures the when
+     * removing entries based on maximum entries, most recently used
+     * is accurate or when expiring, the timestamp is up-to-date.
+     *
+     * @param {string} url
+     */
+    updateTimestamp(url: string): Promise<void>;
+    /**
+     * Can be used to check if a URL has expired or not before it's used.
+     *
+     * This requires a look up from IndexedDB, so can be slow.
+     *
+     * Note: This method will not remove the cached entry, call
+     * `expireEntries()` to remove indexedDB and Cache entries.
+     *
+     * @param {string} url
+     * @return {boolean}
+     */
+    isURLExpired(url: string): Promise<boolean>;
+    /**
+     * Removes the IndexedDB object store used to keep track of cache expiration
+     * metadata.
+     */
+    delete(): Promise<void>;
+}
+export { CacheExpiration };