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/ajv/dist/vocabularies/applicator/additionalItems.d.ts

@@ -0,0 +1,8 @@
+import type { CodeKeywordDefinition, ErrorObject, AnySchema } from "../../types";
+import type { KeywordCxt } from "../../compile/validate";
+export type AdditionalItemsError = ErrorObject<"additionalItems", {
+    limit: number;
+}, AnySchema>;
+declare const def: CodeKeywordDefinition;
+export declare function validateAdditionalItems(cxt: KeywordCxt, items: AnySchema[]): void;
+export default def;