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-build/build/lib/get-file-hash.js

@@ -0,0 +1,27 @@
+"use strict";
+/*
+  Copyright 2018 Google LLC
+
+  Use of this source code is governed by an MIT-style
+  license that can be found in the LICENSE file or at
+  https://opensource.org/licenses/MIT.
+*/
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.getFileHash = void 0;
+const fs_extra_1 = __importDefault(require("fs-extra"));
+const get_string_hash_1 = require("./get-string-hash");
+const errors_1 = require("./errors");
+function getFileHash(file) {
+    try {
+        const buffer = fs_extra_1.default.readFileSync(file);
+        return (0, get_string_hash_1.getStringHash)(buffer);
+    }
+    catch (err) {
+        throw new Error(errors_1.errors['unable-to-get-file-hash'] +
+            ` '${err instanceof Error && err.message ? err.message : ''}'`);
+    }
+}
+exports.getFileHash = getFileHash;