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-range-requests/utils/parseRangeHeader.js

@@ -0,0 +1,47 @@
+/*
+  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.
+*/
+import { WorkboxError } from 'workbox-core/_private/WorkboxError.js';
+import { assert } from 'workbox-core/_private/assert.js';
+import '../_version.js';
+/**
+ * @param {string} rangeHeader A Range: header value.
+ * @return {Object} An object with `start` and `end` properties, reflecting
+ * the parsed value of the Range: header. If either the `start` or `end` are
+ * omitted, then `null` will be returned.
+ *
+ * @private
+ */
+function parseRangeHeader(rangeHeader) {
+    if (process.env.NODE_ENV !== 'production') {
+        assert.isType(rangeHeader, 'string', {
+            moduleName: 'workbox-range-requests',
+            funcName: 'parseRangeHeader',
+            paramName: 'rangeHeader',
+        });
+    }
+    const normalizedRangeHeader = rangeHeader.trim().toLowerCase();
+    if (!normalizedRangeHeader.startsWith('bytes=')) {
+        throw new WorkboxError('unit-must-be-bytes', { normalizedRangeHeader });
+    }
+    // Specifying multiple ranges separate by commas is valid syntax, but this
+    // library only attempts to handle a single, contiguous sequence of bytes.
+    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Range#Syntax
+    if (normalizedRangeHeader.includes(',')) {
+        throw new WorkboxError('single-range-only', { normalizedRangeHeader });
+    }
+    const rangeParts = /(\d*)-(\d*)/.exec(normalizedRangeHeader);
+    // We need either at least one of the start or end values.
+    if (!rangeParts || !(rangeParts[1] || rangeParts[2])) {
+        throw new WorkboxError('invalid-range-values', { normalizedRangeHeader });
+    }
+    return {
+        start: rangeParts[1] === '' ? undefined : Number(rangeParts[1]),
+        end: rangeParts[2] === '' ? undefined : Number(rangeParts[2]),
+    };
+}
+export { parseRangeHeader };