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/mkdirs/index.js

@@ -0,0 +1,14 @@
+'use strict'
+const u = require('universalify').fromPromise
+const { makeDir: _makeDir, makeDirSync } = require('./make-dir')
+const makeDir = u(_makeDir)
+
+module.exports = {
+  mkdirs: makeDir,
+  mkdirsSync: makeDirSync,
+  // alias
+  mkdirp: makeDir,
+  mkdirpSync: makeDirSync,
+  ensureDir: makeDir,
+  ensureDirSync: makeDirSync
+}

pwa/node_modules/fs-extra/lib/mkdirs/make-dir.js

@@ -0,0 +1,141 @@
+// Adapted from https://github.com/sindresorhus/make-dir
+// Copyright (c) Sindre Sorhus <sindresorhus@gmail.com> (sindresorhus.com)
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+// The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+'use strict'
+const fs = require('../fs')
+const path = require('path')
+const atLeastNode = require('at-least-node')
+
+const useNativeRecursiveOption = atLeastNode('10.12.0')
+
+// https://github.com/nodejs/node/issues/8987
+// https://github.com/libuv/libuv/pull/1088
+const checkPath = pth => {
+  if (process.platform === 'win32') {
+    const pathHasInvalidWinCharacters = /[<>:"|?*]/.test(pth.replace(path.parse(pth).root, ''))
+
+    if (pathHasInvalidWinCharacters) {
+      const error = new Error(`Path contains invalid characters: ${pth}`)
+      error.code = 'EINVAL'
+      throw error
+    }
+  }
+}
+
+const processOptions = options => {
+  const defaults = { mode: 0o777 }
+  if (typeof options === 'number') options = { mode: options }
+  return { ...defaults, ...options }
+}
+
+const permissionError = pth => {
+  // This replicates the exception of `fs.mkdir` with native the
+  // `recusive` option when run on an invalid drive under Windows.
+  const error = new Error(`operation not permitted, mkdir '${pth}'`)
+  error.code = 'EPERM'
+  error.errno = -4048
+  error.path = pth
+  error.syscall = 'mkdir'
+  return error
+}
+
+module.exports.makeDir = async (input, options) => {
+  checkPath(input)
+  options = processOptions(options)
+
+  if (useNativeRecursiveOption) {
+    const pth = path.resolve(input)
+
+    return fs.mkdir(pth, {
+      mode: options.mode,
+      recursive: true
+    })
+  }
+
+  const make = async pth => {
+    try {
+      await fs.mkdir(pth, options.mode)
+    } catch (error) {
+      if (error.code === 'EPERM') {
+        throw error
+      }
+
+      if (error.code === 'ENOENT') {
+        if (path.dirname(pth) === pth) {
+          throw permissionError(pth)
+        }
+
+        if (error.message.includes('null bytes')) {
+          throw error
+        }
+
+        await make(path.dirname(pth))
+        return make(pth)
+      }
+
+      try {
+        const stats = await fs.stat(pth)
+        if (!stats.isDirectory()) {
+          // This error is never exposed to the user
+          // it is caught below, and the original error is thrown
+          throw new Error('The path is not a directory')
+        }
+      } catch {
+        throw error
+      }
+    }
+  }
+
+  return make(path.resolve(input))
+}
+
+module.exports.makeDirSync = (input, options) => {
+  checkPath(input)
+  options = processOptions(options)
+
+  if (useNativeRecursiveOption) {
+    const pth = path.resolve(input)
+
+    return fs.mkdirSync(pth, {
+      mode: options.mode,
+      recursive: true
+    })
+  }
+
+  const make = pth => {
+    try {
+      fs.mkdirSync(pth, options.mode)
+    } catch (error) {
+      if (error.code === 'EPERM') {
+        throw error
+      }
+
+      if (error.code === 'ENOENT') {
+        if (path.dirname(pth) === pth) {
+          throw permissionError(pth)
+        }
+
+        if (error.message.includes('null bytes')) {
+          throw error
+        }
+
+        make(path.dirname(pth))
+        return make(pth)
+      }
+
+      try {
+        if (!fs.statSync(pth).isDirectory()) {
+          // This error is never exposed to the user
+          // it is caught below, and the original error is thrown
+          throw new Error('The path is not a directory')
+        }
+      } catch {
+        throw error
+      }
+    }
+  }
+
+  return make(path.resolve(input))
+}