fix: service worker cache busting — unregister old sw on load, bump cache version, stop caching HTML

- Bump sw.js cache from v2 to v3
- Unregister all old service workers on page load
- Stop caching HTML/navigation (caused stale CSS refs after rebuild)

src/components/pwa-register.tsx

@@ -2,12 +2,19 @@
 
 import { useEffect } from "react";
 
-/** Registers the service worker (PWA) once, after hydration. No-op on failure. */
+const SW_VERSION = "3";
+
 export function PwaRegister() {
 	useEffect(() => {
-		if (typeof navigator !== "undefined" && "serviceWorker" in navigator) {
-			navigator.serviceWorker.register("/sw.js").catch(() => {});
-		}
+		if (typeof navigator === "undefined" || !("serviceWorker" in navigator)) return;
+
+		navigator.serviceWorker.getRegistrations().then((regs) => {
+			for (const reg of regs) {
+				reg.unregister();
+			}
+		});
+
+		navigator.serviceWorker.register("/sw.js?" + SW_VERSION).catch(() => {});
 	}, []);
 	return null;
 }