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/strip-comments/lib/Node.js

@@ -0,0 +1,28 @@
+'use strict';
+
+class Node {
+  constructor(node) {
+    this.type = node.type;
+    if (node.value) this.value = node.value;
+    if (node.match) this.match = node.match;
+    this.newline = node.newline || '';
+  }
+  get protected() {
+    return Boolean(this.match) && this.match[1] === '!';
+  }
+}
+
+class Block extends Node {
+  constructor(node) {
+    super(node);
+    this.nodes = node.nodes || [];
+  }
+  push(node) {
+    this.nodes.push(node);
+  }
+  get protected() {
+    return this.nodes.length > 0 && this.nodes[0].protected === true;
+  }
+}
+
+module.exports = { Node, Block };