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/nanoid/async/index.d.ts

@@ -0,0 +1,56 @@
+/**
+ * Generate secure URL-friendly unique ID. The non-blocking version.
+ *
+ * By default, the ID will have 21 symbols to have a collision probability
+ * similar to UUID v4.
+ *
+ * ```js
+ * import { nanoid } from 'nanoid/async'
+ * nanoid().then(id => {
+ *   model.id = id
+ * })
+ * ```
+ *
+ * @param size Size of the ID. The default size is 21.
+ * @returns A promise with a random string.
+ */
+export function nanoid(size?: number): Promise<string>
+
+/**
+ * A low-level function.
+ * Generate secure unique ID with custom alphabet. The non-blocking version.
+ *
+ * Alphabet must contain 256 symbols or less. Otherwise, the generator
+ * will not be secure.
+ *
+ * @param alphabet Alphabet used to generate the ID.
+ * @param defaultSize Size of the ID. The default size is 21.
+ * @returns A function that returns a promise with a random string.
+ *
+ * ```js
+ * import { customAlphabet } from 'nanoid/async'
+ * const nanoid = customAlphabet('0123456789абвгдеё', 5)
+ * nanoid().then(id => {
+ *   model.id = id //=> "8ё56а"
+ * })
+ * ```
+ */
+export function customAlphabet(
+  alphabet: string,
+  defaultSize?: number
+): (size?: number) => Promise<string>
+
+/**
+ * Generate an array of random bytes collected from hardware noise.
+ *
+ * ```js
+ * import { random } from 'nanoid/async'
+ * random(5).then(bytes => {
+ *   bytes //=> [10, 67, 212, 67, 89]
+ * })
+ * ```
+ *
+ * @param bytes Size of the array.
+ * @returns A promise with a random bytes array.
+ */
+export function random(bytes: number): Promise<Uint8Array>