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/terser/PATRONS.md

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+# Our patrons
+
+These are the first-tier patrons from Patreon (notice: **The Terser Patreon is shutting down in favor of opencollective**). My appreciation goes to everyone on this list for supporting the project!
+
+ * 38elements
+ * Alan Orozco
+ * Aria Buckles
+ * CKEditor
+ * Mariusz Nowak
+ * Nakshatra Mukhopadhyay
+ * Philippe Léger
+ * Piotrek Koszuliński
+ * Serhiy Shyyko
+ * Viktor Hubert
+ * 龙腾道