feat: add pwa manifest and service worker

Wire up a production service worker and web app manifest with install metadata and icon assets.
Bump project version to 2.1.0 and register the worker from the main page for offline-ready behavior.

Made-with: Cursor

public/sw.js

@@ -0,0 +1,68 @@
+const CACHE_NAME = 'bscscore-v2.1.0';
+const APP_SHELL = [
+  '/',
+  '/index.html',
+  '/manifest.webmanifest',
+  '/favicon.ico',
+  '/icon-192.png',
+  '/icon-512.png',
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)),
+  );
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys.map((key) => {
+          if (key !== CACHE_NAME) {
+            return caches.delete(key);
+          }
+          return Promise.resolve();
+        }),
+      ),
+    ),
+  );
+  self.clients.claim();
+});
+
+self.addEventListener('fetch', (event) => {
+  const { request } = event;
+  const requestUrl = new URL(request.url);
+
+  if (request.method !== 'GET' || requestUrl.origin !== self.location.origin) {
+    return;
+  }
+
+  if (request.mode === 'navigate') {
+    event.respondWith(
+      fetch(request)
+        .then((response) => {
+          const responseClone = response.clone();
+          caches.open(CACHE_NAME).then((cache) => cache.put(request, responseClone));
+          return response;
+        })
+        .catch(() => caches.match(request).then((cached) => cached || caches.match('/'))),
+    );
+    return;
+  }
+
+  event.respondWith(
+    caches.match(request).then((cachedResponse) => {
+      if (cachedResponse) {
+        return cachedResponse;
+      }
+
+      return fetch(request).then((networkResponse) => {
+        const networkClone = networkResponse.clone();
+        caches.open(CACHE_NAME).then((cache) => cache.put(request, networkClone));
+        return networkResponse;
+      });
+    }),
+  );
+});