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/enum.ts

@@ -0,0 +1,45 @@
+import type {CodeKeywordDefinition, KeywordErrorDefinition, ErrorObject} from "../../types"
+import type {KeywordCxt} from "../../compile/validate"
+import {_, or, and, Code} from "../../compile/codegen"
+import {checkMetadata} from "./metadata"
+import {checkNullable} from "./nullable"
+
+export type JTDEnumError = ErrorObject<"enum", {allowedValues: string[]}, string[]>
+
+const error: KeywordErrorDefinition = {
+  message: "must be equal to one of the allowed values",
+  params: ({schemaCode}) => _`{allowedValues: ${schemaCode}}`,
+}
+
+const def: CodeKeywordDefinition = {
+  keyword: "enum",
+  schemaType: "array",
+  error,
+  code(cxt: KeywordCxt) {
+    checkMetadata(cxt)
+    const {gen, data, schema, schemaValue, parentSchema, it} = cxt
+    if (schema.length === 0) throw new Error("enum must have non-empty array")
+    if (schema.length !== new Set(schema).size) throw new Error("enum items must be unique")
+    let valid: Code
+    const isString = _`typeof ${data} == "string"`
+    if (schema.length >= it.opts.loopEnum) {
+      let cond: Code
+      ;[valid, cond] = checkNullable(cxt, isString)
+      gen.if(cond, loopEnum)
+    } else {
+      /* istanbul ignore if */
+      if (!Array.isArray(schema)) throw new Error("ajv implementation error")
+      valid = and(isString, or(...schema.map((value: string) => _`${data} === ${value}`)))
+      if (parentSchema.nullable) valid = or(_`${data} === null`, valid)
+    }
+    cxt.pass(valid)
+
+    function loopEnum(): void {
+      gen.forOf("v", schemaValue as Code, (v) =>
+        gen.if(_`${valid} = ${data} === ${v}`, () => gen.break())
+      )
+    }
+  },
+}
+
+export default def