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/@rollup/rollup-linux-x64-gnu/README.md

@@ -0,0 +1,3 @@
+# `@rollup/rollup-linux-x64-gnu`
+
+This is the **x86_64-unknown-linux-gnu** binary for `rollup`

pwa/node_modules/@rollup/rollup-linux-x64-gnu/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@rollup/rollup-linux-x64-gnu",
+  "version": "4.59.0",
+  "os": [
+    "linux"
+  ],
+  "cpu": [
+    "x64"
+  ],
+  "files": [
+    "rollup.linux-x64-gnu.node"
+  ],
+  "description": "Native bindings for Rollup",
+  "author": "Lukas Taegert-Atkinson",
+  "homepage": "https://rollupjs.org/",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/rollup/rollup.git"
+  },
+  "libc": [
+    "glibc"
+  ],
+  "main": "./rollup.linux-x64-gnu.node"
+}