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/calculateEffectiveBoundaries.js

@@ -0,0 +1,57 @@
+/*
+  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 {Blob} blob A source blob.
+ * @param {number} [start] The offset to use as the start of the
+ * slice.
+ * @param {number} [end] The offset to use as the end of the slice.
+ * @return {Object} An object with `start` and `end` properties, reflecting
+ * the effective boundaries to use given the size of the blob.
+ *
+ * @private
+ */
+function calculateEffectiveBoundaries(blob, start, end) {
+    if (process.env.NODE_ENV !== 'production') {
+        assert.isInstance(blob, Blob, {
+            moduleName: 'workbox-range-requests',
+            funcName: 'calculateEffectiveBoundaries',
+            paramName: 'blob',
+        });
+    }
+    const blobSize = blob.size;
+    if ((end && end > blobSize) || (start && start < 0)) {
+        throw new WorkboxError('range-not-satisfiable', {
+            size: blobSize,
+            end,
+            start,
+        });
+    }
+    let effectiveStart;
+    let effectiveEnd;
+    if (start !== undefined && end !== undefined) {
+        effectiveStart = start;
+        // Range values are inclusive, so add 1 to the value.
+        effectiveEnd = end + 1;
+    }
+    else if (start !== undefined && end === undefined) {
+        effectiveStart = start;
+        effectiveEnd = blobSize;
+    }
+    else if (end !== undefined && start === undefined) {
+        effectiveStart = blobSize - end;
+        effectiveEnd = blobSize;
+    }
+    return {
+        start: effectiveStart,
+        end: effectiveEnd,
+    };
+}
+export { calculateEffectiveBoundaries };