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/compile/validate/applicability.ts

@@ -0,0 +1,22 @@
+import type {AnySchemaObject} from "../../types"
+import type {SchemaObjCxt} from ".."
+import type {JSONType, RuleGroup, Rule} from "../rules"
+
+export function schemaHasRulesForType(
+  {schema, self}: SchemaObjCxt,
+  type: JSONType
+): boolean | undefined {
+  const group = self.RULES.types[type]
+  return group && group !== true && shouldUseGroup(schema, group)
+}
+
+export function shouldUseGroup(schema: AnySchemaObject, group: RuleGroup): boolean {
+  return group.rules.some((rule) => shouldUseRule(schema, rule))
+}
+
+export function shouldUseRule(schema: AnySchemaObject, rule: Rule): boolean | undefined {
+  return (
+    schema[rule.keyword] !== undefined ||
+    rule.definition.implements?.some((kwd) => schema[kwd] !== undefined)
+  )
+}