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/source-map/lib/wasm.js

@@ -0,0 +1,107 @@
+const readWasm = require("../lib/read-wasm");
+
+/**
+ * Provide the JIT with a nice shape / hidden class.
+ */
+function Mapping() {
+  this.generatedLine = 0;
+  this.generatedColumn = 0;
+  this.lastGeneratedColumn = null;
+  this.source = null;
+  this.originalLine = null;
+  this.originalColumn = null;
+  this.name = null;
+}
+
+let cachedWasm = null;
+
+module.exports = function wasm() {
+  if (cachedWasm) {
+    return cachedWasm;
+  }
+
+  const callbackStack = [];
+
+  cachedWasm = readWasm().then(buffer => {
+      return WebAssembly.instantiate(buffer, {
+        env: {
+          mapping_callback(
+            generatedLine,
+            generatedColumn,
+
+            hasLastGeneratedColumn,
+            lastGeneratedColumn,
+
+            hasOriginal,
+            source,
+            originalLine,
+            originalColumn,
+
+            hasName,
+            name
+          ) {
+            const mapping = new Mapping();
+            // JS uses 1-based line numbers, wasm uses 0-based.
+            mapping.generatedLine = generatedLine + 1;
+            mapping.generatedColumn = generatedColumn;
+
+            if (hasLastGeneratedColumn) {
+              // JS uses inclusive last generated column, wasm uses exclusive.
+              mapping.lastGeneratedColumn = lastGeneratedColumn - 1;
+            }
+
+            if (hasOriginal) {
+              mapping.source = source;
+              // JS uses 1-based line numbers, wasm uses 0-based.
+              mapping.originalLine = originalLine + 1;
+              mapping.originalColumn = originalColumn;
+
+              if (hasName) {
+                mapping.name = name;
+              }
+            }
+
+            callbackStack[callbackStack.length - 1](mapping);
+          },
+
+          start_all_generated_locations_for() { console.time("all_generated_locations_for"); },
+          end_all_generated_locations_for() { console.timeEnd("all_generated_locations_for"); },
+
+          start_compute_column_spans() { console.time("compute_column_spans"); },
+          end_compute_column_spans() { console.timeEnd("compute_column_spans"); },
+
+          start_generated_location_for() { console.time("generated_location_for"); },
+          end_generated_location_for() { console.timeEnd("generated_location_for"); },
+
+          start_original_location_for() { console.time("original_location_for"); },
+          end_original_location_for() { console.timeEnd("original_location_for"); },
+
+          start_parse_mappings() { console.time("parse_mappings"); },
+          end_parse_mappings() { console.timeEnd("parse_mappings"); },
+
+          start_sort_by_generated_location() { console.time("sort_by_generated_location"); },
+          end_sort_by_generated_location() { console.timeEnd("sort_by_generated_location"); },
+
+          start_sort_by_original_location() { console.time("sort_by_original_location"); },
+          end_sort_by_original_location() { console.timeEnd("sort_by_original_location"); },
+        }
+      });
+  }).then(Wasm => {
+    return {
+      exports: Wasm.instance.exports,
+      withMappingCallback: (mappingCallback, f) => {
+        callbackStack.push(mappingCallback);
+        try {
+          f();
+        } finally {
+          callbackStack.pop();
+        }
+      }
+    };
+  }).then(null, e => {
+    cachedWasm = null;
+    throw e;
+  });
+
+  return cachedWasm;
+};