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/applicator/items2020.ts

@@ -0,0 +1,36 @@
+import type {
+  CodeKeywordDefinition,
+  KeywordErrorDefinition,
+  ErrorObject,
+  AnySchema,
+} from "../../types"
+import type {KeywordCxt} from "../../compile/validate"
+import {_, str} from "../../compile/codegen"
+import {alwaysValidSchema} from "../../compile/util"
+import {validateArray} from "../code"
+import {validateAdditionalItems} from "./additionalItems"
+
+export type ItemsError = ErrorObject<"items", {limit: number}, AnySchema>
+
+const error: KeywordErrorDefinition = {
+  message: ({params: {len}}) => str`must NOT have more than ${len} items`,
+  params: ({params: {len}}) => _`{limit: ${len}}`,
+}
+
+const def: CodeKeywordDefinition = {
+  keyword: "items",
+  type: "array",
+  schemaType: ["object", "boolean"],
+  before: "uniqueItems",
+  error,
+  code(cxt: KeywordCxt) {
+    const {schema, parentSchema, it} = cxt
+    const {prefixItems} = parentSchema
+    it.items = true
+    if (alwaysValidSchema(it, schema)) return
+    if (prefixItems) validateAdditionalItems(cxt, prefixItems)
+    else cxt.ok(validateArray(cxt))
+  },
+}
+
+export default def