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/assertion-error/index.js

@@ -0,0 +1,60 @@
+// deno-fmt-ignore-file
+// deno-lint-ignore-file
+// This code was bundled using `deno bundle` and it's not recommended to edit it manually
+
+const canElideFrames = "captureStackTrace" in Error;
+class AssertionError extends Error {
+    message;
+    get name() {
+        return "AssertionError";
+    }
+    get ok() {
+        return false;
+    }
+    constructor(message = "Unspecified AssertionError", props, ssf){
+        super(message);
+        this.message = message;
+        if (canElideFrames) {
+            Error.captureStackTrace(this, ssf || AssertionError);
+        }
+        for(const key in props){
+            if (!(key in this)) {
+                this[key] = props[key];
+            }
+        }
+    }
+    toJSON(stack) {
+        return {
+            ...this,
+            name: this.name,
+            message: this.message,
+            ok: false,
+            stack: stack !== false ? this.stack : undefined
+        };
+    }
+}
+class AssertionResult {
+    get name() {
+        return "AssertionResult";
+    }
+    get ok() {
+        return true;
+    }
+    constructor(props){
+        for(const key in props){
+            if (!(key in this)) {
+                this[key] = props[key];
+            }
+        }
+    }
+    toJSON() {
+        return {
+            ...this,
+            name: this.name,
+            ok: this.ok
+        };
+    }
+}
+export { AssertionError as AssertionError };
+export { AssertionResult as AssertionResult };
+