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/elements.ts

@@ -0,0 +1,32 @@
+import type {CodeKeywordDefinition, SchemaObject} from "../../types"
+import type {KeywordCxt} from "../../compile/validate"
+import {alwaysValidSchema} from "../../compile/util"
+import {validateArray} from "../code"
+import {_, not} from "../../compile/codegen"
+import {checkMetadata} from "./metadata"
+import {checkNullable} from "./nullable"
+import {typeError, _JTDTypeError} from "./error"
+
+export type JTDElementsError = _JTDTypeError<"elements", "array", SchemaObject>
+
+const def: CodeKeywordDefinition = {
+  keyword: "elements",
+  schemaType: "object",
+  error: typeError("array"),
+  code(cxt: KeywordCxt) {
+    checkMetadata(cxt)
+    const {gen, data, schema, it} = cxt
+    if (alwaysValidSchema(it, schema)) return
+    const [valid] = checkNullable(cxt)
+    gen.if(not(valid), () =>
+      gen.if(
+        _`Array.isArray(${data})`,
+        () => gen.assign(valid, validateArray(cxt)),
+        () => cxt.error()
+      )
+    )
+    cxt.ok(valid)
+  },
+}
+
+export default def