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/foreground-child/dist/esm/proxy-signals.js

@@ -0,0 +1,34 @@
+import { allSignals } from './all-signals.js';
+/**
+ * Starts forwarding signals to `child` through `parent`.
+ */
+export const proxySignals = (child) => {
+    const listeners = new Map();
+    for (const sig of allSignals) {
+        const listener = () => {
+            // some signals can only be received, not sent
+            try {
+                child.kill(sig);
+                /* c8 ignore start */
+            }
+            catch (_) { }
+            /* c8 ignore stop */
+        };
+        try {
+            // if it's a signal this system doesn't recognize, skip it
+            process.on(sig, listener);
+            listeners.set(sig, listener);
+            /* c8 ignore start */
+        }
+        catch (_) { }
+        /* c8 ignore stop */
+    }
+    const unproxy = () => {
+        for (const [sig, listener] of listeners) {
+            process.removeListener(sig, listener);
+        }
+    };
+    child.on('exit', unproxy);
+    return unproxy;
+};
+//# sourceMappingURL=proxy-signals.js.map