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-cacheable-response/CacheableResponse.d.ts

@@ -0,0 +1,45 @@
+import './_version.js';
+export interface CacheableResponseOptions {
+    statuses?: number[];
+    headers?: {
+        [headerName: string]: string;
+    };
+}
+/**
+ * This class allows you to set up rules determining what
+ * status codes and/or headers need to be present in order for a
+ * [`Response`](https://developer.mozilla.org/en-US/docs/Web/API/Response)
+ * to be considered cacheable.
+ *
+ * @memberof workbox-cacheable-response
+ */
+declare class CacheableResponse {
+    private readonly _statuses?;
+    private readonly _headers?;
+    /**
+     * To construct a new CacheableResponse instance you must provide at least
+     * one of the `config` properties.
+     *
+     * If both `statuses` and `headers` are specified, then both conditions must
+     * be met for the `Response` to be considered cacheable.
+     *
+     * @param {Object} config
+     * @param {Array<number>} [config.statuses] One or more status codes that a
+     * `Response` can have and be considered cacheable.
+     * @param {Object<string,string>} [config.headers] A mapping of header names
+     * and expected values that a `Response` can have and be considered cacheable.
+     * If multiple headers are provided, only one needs to be present.
+     */
+    constructor(config?: CacheableResponseOptions);
+    /**
+     * Checks a response to see whether it's cacheable or not, based on this
+     * object's configuration.
+     *
+     * @param {Response} response The response whose cacheability is being
+     * checked.
+     * @return {boolean} `true` if the `Response` is cacheable, and `false`
+     * otherwise.
+     */
+    isResponseCacheable(response: Response): boolean;
+}
+export { CacheableResponse };