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/vocabularies/jtd/error.ts

@@ -0,0 +1,23 @@
+import type {KeywordErrorDefinition, KeywordErrorCxt, ErrorObject} from "../../types"
+import {_, Code} from "../../compile/codegen"
+
+export type _JTDTypeError<K extends string, T extends string, S> = ErrorObject<
+  K,
+  {type: T; nullable: boolean},
+  S
+>
+
+export function typeError(t: string): KeywordErrorDefinition {
+  return {
+    message: (cxt) => typeErrorMessage(cxt, t),
+    params: (cxt) => typeErrorParams(cxt, t),
+  }
+}
+
+export function typeErrorMessage({parentSchema}: KeywordErrorCxt, t: string): string {
+  return parentSchema?.nullable ? `must be ${t} or null` : `must be ${t}`
+}
+
+export function typeErrorParams({parentSchema}: KeywordErrorCxt, t: string): Code {
+  return _`{type: ${t}, nullable: ${!!parentSchema?.nullable}}`
+}