Initial commit: Shelem card game

Full-stack multiplayer Shelem (Iranian trick-taking card game) with
Socket.IO, JWT auth, bot players, joker mode, and mobile-friendly UI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/sw.js

@@ -0,0 +1,57 @@
+'use strict';
+const CACHE_NAME = 'shelem-v1';
+
+const PRECACHE = [
+  '/',
+  '/index.html',
+  '/style.css',
+  '/app.js',
+  '/manifest.json',
+  '/icons/icon-192.png',
+  '/icons/icon-512.png',
+  '/icons/icon.svg',
+];
+
+self.addEventListener('install', event => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then(cache => cache.addAll(PRECACHE))
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', event => {
+  event.waitUntil(
+    caches.keys().then(keys =>
+      Promise.all(keys.filter(k => k !== CACHE_NAME).map(k => caches.delete(k)))
+    )
+  );
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', event => {
+  const url = event.request.url;
+  if (event.request.method !== 'GET') return;
+  if (url.includes('/socket.io/')) return;
+
+  if (url.includes('/cards/')) {
+    event.respondWith(
+      caches.match(event.request).then(cached => {
+        if (cached) return cached;
+        return fetch(event.request).then(res => {
+          caches.open(CACHE_NAME).then(c => c.put(event.request, res.clone()));
+          return res;
+        });
+      })
+    );
+    return;
+  }
+
+  event.respondWith(
+    fetch(event.request)
+      .then(res => {
+        caches.open(CACHE_NAME).then(c => c.put(event.request, res.clone()));
+        return res;
+      })
+      .catch(() => caches.match(event.request))
+  );
+});