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/fs-extra/lib/ensure/symlink.js

@@ -0,0 +1,63 @@
+'use strict'
+
+const u = require('universalify').fromCallback
+const path = require('path')
+const fs = require('graceful-fs')
+const _mkdirs = require('../mkdirs')
+const mkdirs = _mkdirs.mkdirs
+const mkdirsSync = _mkdirs.mkdirsSync
+
+const _symlinkPaths = require('./symlink-paths')
+const symlinkPaths = _symlinkPaths.symlinkPaths
+const symlinkPathsSync = _symlinkPaths.symlinkPathsSync
+
+const _symlinkType = require('./symlink-type')
+const symlinkType = _symlinkType.symlinkType
+const symlinkTypeSync = _symlinkType.symlinkTypeSync
+
+const pathExists = require('../path-exists').pathExists
+
+function createSymlink (srcpath, dstpath, type, callback) {
+  callback = (typeof type === 'function') ? type : callback
+  type = (typeof type === 'function') ? false : type
+
+  pathExists(dstpath, (err, destinationExists) => {
+    if (err) return callback(err)
+    if (destinationExists) return callback(null)
+    symlinkPaths(srcpath, dstpath, (err, relative) => {
+      if (err) return callback(err)
+      srcpath = relative.toDst
+      symlinkType(relative.toCwd, type, (err, type) => {
+        if (err) return callback(err)
+        const dir = path.dirname(dstpath)
+        pathExists(dir, (err, dirExists) => {
+          if (err) return callback(err)
+          if (dirExists) return fs.symlink(srcpath, dstpath, type, callback)
+          mkdirs(dir, err => {
+            if (err) return callback(err)
+            fs.symlink(srcpath, dstpath, type, callback)
+          })
+        })
+      })
+    })
+  })
+}
+
+function createSymlinkSync (srcpath, dstpath, type) {
+  const destinationExists = fs.existsSync(dstpath)
+  if (destinationExists) return undefined
+
+  const relative = symlinkPathsSync(srcpath, dstpath)
+  srcpath = relative.toDst
+  type = symlinkTypeSync(relative.toCwd, type)
+  const dir = path.dirname(dstpath)
+  const exists = fs.existsSync(dir)
+  if (exists) return fs.symlinkSync(srcpath, dstpath, type)
+  mkdirsSync(dir)
+  return fs.symlinkSync(srcpath, dstpath, type)
+}
+
+module.exports = {
+  createSymlink: u(createSymlink),
+  createSymlinkSync
+}