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/leaflet.offline/karma.conf.ts

@@ -0,0 +1,92 @@
+const typescript = require('@rollup/plugin-typescript');
+const { nodeResolve } = require('@rollup/plugin-node-resolve');
+const commonjs = require('@rollup/plugin-commonjs');
+const istanbul = require('rollup-plugin-istanbul');
+
+const extensions = ['.js', '.ts'];
+
+process.env.CHROME_BIN = require('puppeteer').executablePath()
+
+module.exports = (config) => {
+  config.set({
+    // base path that will be used to resolve all patterns (eg. files, exclude)
+    basePath: '',
+
+    // frameworks to use
+    // available frameworks: https://npmjs.org/browse/keyword/karma-adapter
+    frameworks: ['mocha'],
+
+    // list of files / patterns to load in the browser
+    files: ['test/*.ts'],
+
+    // list of files to exclude
+    exclude: [],
+
+    // preprocess matching files before serving them to the browser
+    // available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
+    preprocessors: {
+      'test/*.ts': ['rollup'],
+    },
+    rollupPreprocessor: {
+      output: {
+        format: 'iife',
+        name: 'LeafletOffline',
+        sourcemap: 'inline',
+      },
+      plugins: [
+        commonjs(),
+        nodeResolve({ extensions }),
+        typescript({ declaration: false, declarationDir: undefined }),
+        istanbul({ exclude: ['test/*.ts', 'node_modules/**/*'] }),
+      ],
+    },
+
+    // test results reporter to use
+    // possible values: 'dots', 'progress'
+    // available reporters: https://npmjs.org/browse/keyword/karma-reporter
+    reporters: ['mocha', 'progress', 'coverage'],
+
+    // web server port
+    port: 9876,
+
+    // enable / disable colors in the output (reporters and logs)
+    colors: true,
+
+    // level of logging
+    // possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
+    logLevel: config.LOG_INFO,
+
+    // enable / disable watching file and executing tests whenever any file changes
+    autoWatch: true,
+
+    // start these browsers
+    // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
+    browsers: ['ChromeHeadless','ChromeHeadlessWithoutSandbox'],
+
+    // Continuous Integration mode
+    // if true, Karma captures browsers, runs the tests and exits
+    singleRun: true,
+
+    // Concurrency level
+    // how many browser should be started simultaneous
+    concurrency: Infinity,
+
+    // damn ubuntu snap https://github.com/karma-runner/karma-firefox-launcher/issues/183#issuecomment-1283875784
+    customLaunchers: {
+      ChromeHeadlessWithoutSandbox: {
+        base: 'Chrome',
+        flags: ['--no-sandbox','--headless'],
+        displayName: 'Chrome w/o sandbox'
+      }
+    },
+    coverageReporter: {
+      reporters: [
+        {
+          type: 'html',
+          dir: 'coverage/',
+        },
+        { type: 'lcov' },
+      ],
+    },
+  });
+};