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/signal-exit/dist/mjs/index.d.ts

@@ -0,0 +1,48 @@
+/// <reference types="node" />
+import { signals } from './signals.js';
+export { signals };
+/**
+ * A function that takes an exit code and signal as arguments
+ *
+ * In the case of signal exits *only*, a return value of true
+ * will indicate that the signal is being handled, and we should
+ * not synthetically exit with the signal we received. Regardless
+ * of the handler return value, the handler is unloaded when an
+ * otherwise fatal signal is received, so you get exactly 1 shot
+ * at it, unless you add another onExit handler at that point.
+ *
+ * In the case of numeric code exits, we may already have committed
+ * to exiting the process, for example via a fatal exception or
+ * unhandled promise rejection, so it is impossible to stop safely.
+ */
+export type Handler = (code: number | null | undefined, signal: NodeJS.Signals | null) => true | void;
+export declare const 
+/**
+ * Called when the process is exiting, whether via signal, explicit
+ * exit, or running out of stuff to do.
+ *
+ * If the global process object is not suitable for instrumentation,
+ * then this will be a no-op.
+ *
+ * Returns a function that may be used to unload signal-exit.
+ */
+onExit: (cb: Handler, opts?: {
+    alwaysLast?: boolean | undefined;
+} | undefined) => () => void, 
+/**
+ * Load the listeners.  Likely you never need to call this, unless
+ * doing a rather deep integration with signal-exit functionality.
+ * Mostly exposed for the benefit of testing.
+ *
+ * @internal
+ */
+load: () => void, 
+/**
+ * Unload the listeners.  Likely you never need to call this, unless
+ * doing a rather deep integration with signal-exit functionality.
+ * Mostly exposed for the benefit of testing.
+ *
+ * @internal
+ */
+unload: () => void;
+//# sourceMappingURL=index.d.ts.map