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/siginfo/README.md

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+# `siginfo`
+
+[![Build Status](https://travis-ci.org/emilbayes/siginfo.svg?branch=master)](https://travis-ci.org/eemilbayes/siginfo)
+
+> Utility module to print pretty messages on SIGINFO/SIGUSR1
+
+`SIGINFO` on BSD / macOS and `SIGUSR1` on Linux, usually triggered by
+`Ctrl + T`, are by convention used to print information about
+a long running process internal state. Eg. `dd` will tell you how many blocks it
+has written and at what speed, while `xz` will tell you progress, compression
+ratio and estimated time remaining.
+
+This module wraps both signals, checks if the process is connected to TTY and
+lets you do whatever you want.
+
+## Usage
+
+```js
+var siginfo = require('siginfo')
+var pkg = require('./package.json')
+
+siginfo(function () {
+  console.dir({
+    version: pkg.version,
+    uptime: process.uptime()
+  })
+})
+
+```
+
+## API
+
+### `var removeListener = siginfo(queryFn, [force])`
+
+`queryFn` can be used for whatever you want (logging, sending a UDP message, etc.).
+Setting `force = true` will attach the event handlers whether a TTY is present
+or not.
+
+## Install
+
+```sh
+npm install siginfo
+```
+
+## License
+
+[ISC](LICENSE)