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/which/README.md

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+# which
+
+Like the unix `which` utility.
+
+Finds the first instance of a specified executable in the PATH
+environment variable.  Does not cache the results, so `hash -r` is not
+needed when the PATH changes.
+
+## USAGE
+
+```javascript
+var which = require('which')
+
+// async usage
+which('node', function (er, resolvedPath) {
+  // er is returned if no "node" is found on the PATH
+  // if it is found, then the absolute path to the exec is returned
+})
+
+// or promise
+which('node').then(resolvedPath => { ... }).catch(er => { ... not found ... })
+
+// sync usage
+// throws if not found
+var resolved = which.sync('node')
+
+// if nothrow option is used, returns null if not found
+resolved = which.sync('node', {nothrow: true})
+
+// Pass options to override the PATH and PATHEXT environment vars.
+which('node', { path: someOtherPath }, function (er, resolved) {
+  if (er)
+    throw er
+  console.log('found at %j', resolved)
+})
+```
+
+## CLI USAGE
+
+Same as the BSD `which(1)` binary.
+
+```
+usage: which [-as] program ...
+```
+
+## OPTIONS
+
+You may pass an options object as the second argument.
+
+- `path`: Use instead of the `PATH` environment variable.
+- `pathExt`: Use instead of the `PATHEXT` environment variable.
+- `all`: Return all matches, instead of just the first one.  Note that
+  this means the function returns an array of strings instead of a
+  single string.