Task 96ab3c0b: PWA manifest and service worker (#189)

admin/src/pwa/register.ts

@@ -0,0 +1,13 @@
+/**
+ * Service worker registration for the installable admin PWA.
+ * Registers /sw.js only in production builds, so dev servers and tests never
+ * run a worker. Failures are logged, never thrown — the app works without it.
+ */
+export async function registerServiceWorker(): Promise<void> {
+  if (!import.meta.env.PROD || !("serviceWorker" in navigator)) return;
+  try {
+    await navigator.serviceWorker.register("/sw.js", { scope: "/" });
+  } catch (error) {
+    console.error("Service worker registration failed:", error);
+  }
+}