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/source-map/lib/read-wasm.js

@@ -0,0 +1,25 @@
+"use strict";
+
+// Note: This file is replaced with "read-wasm-browser.js" when this module is
+// bundled with a packager that takes package.json#browser fields into account.
+
+const fs = require("fs");
+const path = require("path");
+
+module.exports = function readWasm() {
+  return new Promise((resolve, reject) => {
+    const wasmPath = path.join(__dirname, "mappings.wasm");
+    fs.readFile(wasmPath, null, (error, data) => {
+      if (error) {
+        reject(error);
+        return;
+      }
+
+      resolve(data.buffer);
+    });
+  });
+};
+
+module.exports.initialize = _ => {
+  console.debug("SourceMapConsumer.initialize is a no-op when running in node.js");
+};