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/lib/refs/json-schema-2020-12/index.ts

@@ -0,0 +1,30 @@
+import type Ajv from "../../core"
+import type {AnySchemaObject} from "../../types"
+import * as metaSchema from "./schema.json"
+import * as applicator from "./meta/applicator.json"
+import * as unevaluated from "./meta/unevaluated.json"
+import * as content from "./meta/content.json"
+import * as core from "./meta/core.json"
+import * as format from "./meta/format-annotation.json"
+import * as metadata from "./meta/meta-data.json"
+import * as validation from "./meta/validation.json"
+
+const META_SUPPORT_DATA = ["/properties"]
+
+export default function addMetaSchema2020(this: Ajv, $data?: boolean): Ajv {
+  ;[
+    metaSchema,
+    applicator,
+    unevaluated,
+    content,
+    core,
+    with$data(this, format),
+    metadata,
+    with$data(this, validation),
+  ].forEach((sch) => this.addMetaSchema(sch, undefined, false))
+  return this
+
+  function with$data(ajv: Ajv, sch: AnySchemaObject): AnySchemaObject {
+    return $data ? ajv.$dataMetaSchema(sch, META_SUPPORT_DATA) : sch
+  }
+}