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)

public/sw.js

@@ -1,5 +1,5 @@
-const CACHE = "atom-v2";
-const API_CACHE = "atom-api-v2";
+const CACHE = "atom-v3";
+const API_CACHE = "atom-api-v3";
 
 self.addEventListener("install", () => self.skipWaiting());
 
@@ -60,14 +60,6 @@ self.addEventListener("fetch", (event) => {
 	}
 
 	if (req.mode === "navigate") {
-		event.respondWith(
-			fetch(req)
-				.then((res) => {
-					const copy = res.clone();
-					caches.open(CACHE).then((c) => c.put(req, copy)).catch(() => {});
-					return res;
-				})
-				.catch(() => caches.match(req).then((hit) => hit || caches.match("/"))),
-		);
+		event.respondWith(fetch(req));
 	}
 });