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/postcss/lib/fromJSON.js

@@ -0,0 +1,54 @@
+'use strict'
+
+let AtRule = require('./at-rule')
+let Comment = require('./comment')
+let Declaration = require('./declaration')
+let Input = require('./input')
+let PreviousMap = require('./previous-map')
+let Root = require('./root')
+let Rule = require('./rule')
+
+function fromJSON(json, inputs) {
+  if (Array.isArray(json)) return json.map(n => fromJSON(n))
+
+  let { inputs: ownInputs, ...defaults } = json
+  if (ownInputs) {
+    inputs = []
+    for (let input of ownInputs) {
+      let inputHydrated = { ...input, __proto__: Input.prototype }
+      if (inputHydrated.map) {
+        inputHydrated.map = {
+          ...inputHydrated.map,
+          __proto__: PreviousMap.prototype
+        }
+      }
+      inputs.push(inputHydrated)
+    }
+  }
+  if (defaults.nodes) {
+    defaults.nodes = json.nodes.map(n => fromJSON(n, inputs))
+  }
+  if (defaults.source) {
+    let { inputId, ...source } = defaults.source
+    defaults.source = source
+    if (inputId != null) {
+      defaults.source.input = inputs[inputId]
+    }
+  }
+  if (defaults.type === 'root') {
+    return new Root(defaults)
+  } else if (defaults.type === 'decl') {
+    return new Declaration(defaults)
+  } else if (defaults.type === 'rule') {
+    return new Rule(defaults)
+  } else if (defaults.type === 'comment') {
+    return new Comment(defaults)
+  } else if (defaults.type === 'atrule') {
+    return new AtRule(defaults)
+  } else {
+    throw new Error('Unknown node type: ' + json.type)
+  }
+}
+
+module.exports = fromJSON
+fromJSON.default = fromJSON