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/json-schema-traverse/index.d.ts

@@ -0,0 +1,40 @@
+declare function traverse(
+  schema: traverse.SchemaObject,
+  opts: traverse.Options,
+  cb?: traverse.Callback
+): void;
+
+declare function traverse(
+  schema: traverse.SchemaObject,
+  cb: traverse.Callback
+): void;
+
+declare namespace traverse {
+  interface SchemaObject {
+    $id?: string;
+    $schema?: string;
+    [x: string]: any;
+  }
+
+  type Callback = (
+    schema: SchemaObject,
+    jsonPtr: string,
+    rootSchema: SchemaObject,
+    parentJsonPtr?: string,
+    parentKeyword?: string,
+    parentSchema?: SchemaObject,
+    keyIndex?: string | number
+  ) => void;
+
+  interface Options {
+    allKeys?: boolean;
+    cb?:
+      | Callback
+      | {
+          pre?: Callback;
+          post?: Callback;
+        };
+  }
+}
+
+export = traverse;