fix(pwa): make web updates deterministic (#1093)

* fix(pwa): make web updates deterministic

* fix(pwa): address review feedback

src/lib/app-update.ts

@@ -0,0 +1,26 @@
+const isElectron = window.electronApi?.isElectron === true;
+
+const fetchLatestStableVersion = async (): Promise<string> => {
+  const versionUrl = isElectron
+    ? 'https://raw.githubusercontent.com/bitsocialnet/5chan/master/package.json'
+    : new URL(`/version.json?t=${Date.now()}`, window.location.origin).toString();
+  const packageRes = await fetch(versionUrl, { cache: 'no-store' });
+  const packageData = await packageRes.json();
+
+  if (typeof packageData?.version !== 'string') {
+    throw new Error('invalid version payload');
+  }
+
+  return packageData.version;
+};
+
+const refreshServiceWorkerRegistration = async (): Promise<void> => {
+  if (!('serviceWorker' in navigator)) {
+    return;
+  }
+
+  const registration = await navigator.serviceWorker.getRegistration();
+  await registration?.update();
+};
+
+export { fetchLatestStableVersion, isElectron, refreshServiceWorkerRegistration };