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/modify-url-prefix-transform.js

@@ -0,0 +1,51 @@
+"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.
+*/
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.modifyURLPrefixTransform = void 0;
+const errors_1 = require("./errors");
+const escape_regexp_1 = require("./escape-regexp");
+function modifyURLPrefixTransform(modifyURLPrefix) {
+    if (!modifyURLPrefix ||
+        typeof modifyURLPrefix !== 'object' ||
+        Array.isArray(modifyURLPrefix)) {
+        throw new Error(errors_1.errors['modify-url-prefix-bad-prefixes']);
+    }
+    // If there are no entries in modifyURLPrefix, just return an identity
+    // function as a shortcut.
+    if (Object.keys(modifyURLPrefix).length === 0) {
+        return (manifest) => {
+            return { manifest };
+        };
+    }
+    for (const key of Object.keys(modifyURLPrefix)) {
+        if (typeof modifyURLPrefix[key] !== 'string') {
+            throw new Error(errors_1.errors['modify-url-prefix-bad-prefixes']);
+        }
+    }
+    // Escape the user input so it's safe to use in a regex.
+    const safeModifyURLPrefixes = Object.keys(modifyURLPrefix).map(escape_regexp_1.escapeRegExp);
+    // Join all the `modifyURLPrefix` keys so a single regex can be used.
+    const prefixMatchesStrings = safeModifyURLPrefixes.join('|');
+    // Add `^` to the front the prefix matches so it only matches the start of
+    // a string.
+    const modifyRegex = new RegExp(`^(${prefixMatchesStrings})`);
+    return (originalManifest) => {
+        const manifest = originalManifest.map((entry) => {
+            if (typeof entry.url !== 'string') {
+                throw new Error(errors_1.errors['manifest-entry-bad-url']);
+            }
+            entry.url = entry.url.replace(modifyRegex, (match) => {
+                return modifyURLPrefix[match];
+            });
+            return entry;
+        });
+        return { manifest };
+    };
+}
+exports.modifyURLPrefixTransform = modifyURLPrefixTransform;