static/sw.js

const CACHE_NAME = 'ghostboard-v1';
const ASSETS = [
  '/',
  '/static/images/icon.svg',
  '/static/manifest.json',
  'https://cdn.tailwindcss.com',
  'https://cdnjs.cloudflare.com/ajax/libs/html2canvas/1.4.1/html2canvas.min.js'
];

self.addEventListener('install', (e) => {
  e.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(ASSETS))
  );
});

self.addEventListener('fetch', (e) => {
  // Network first for HTML (navigation), Cache first for assets
  if (e.request.mode === 'navigate') {
    e.respondWith(
      fetch(e.request).catch(() => {
        return caches.match(e.request).then(response => {
            if (response) return response;
            // Fallback to offline page if I had one, or just root
            return caches.match('/');
        });
      })
    );
  } else {
    e.respondWith(
      caches.match(e.request).then((response) => {
        return response || fetch(e.request);
      })
    );
  }
});