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/tinyspy/README.md

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+# tinyspy
+
+> minimal fork of nanospy, with more features 🕵🏻‍♂️
+
+A `10KB` package for minimal and easy testing with no dependencies.
+This package was created for having a tiny spy library to use in `vitest`, but it can also be used in `jest` and other test environments.
+
+_In case you need more tiny libraries like tinypool or tinyspy, please consider submitting an [RFC](https://github.com/tinylibs/rfcs)_
+
+## Docs
+Read full docs **[here](https://github.com/tinylibs/tinyspy#readme)**.