fix(pwa): stop the service worker replaying chunks from a previous release

The Catalog Studio rendered as a blank white page after a deploy, while the
server was serving it correctly: /admin/studio/furni answered 200 with 110KB
of HTML and every API it calls answered 200 with data. No script chunk 404ed
during the session and no JavaScript threw, so the failure was entirely in
what the browser chose to execute.

The service worker wrapped /assets/ and /_next/static/ in a Cache Storage
entry served cache-first, under a hardcoded name (atom-v3) with no build id
and no revalidation. A release therefore could not invalidate it: the browser
kept replaying the previous release's chunks against the new HTML, and React
never hydrated. The chunk branch also had no .catch(), unlike the API branch
below it, so a rejected fetch silently dropped the <script> instead of
surfacing a network error the browser could retry.

That cache also bought nothing. nginx already sends /_next/static/ and
/assets/ as `max-age=31536000, immutable`, and those filenames are
content-hashed, so the HTTP cache is both sufficient and safe — a changed
file gets a new name. The worker was the only layer able to go stale across a
deploy, and it was the one doing it.

Both prefixes now fall through to the network and are left to the HTTP cache.
The API offline fallback and network-first navigations are unchanged, and the
cache names move to v4 so an existing worker is replaced. SW_VERSION moves
with them: it is part of the registration URL, so without the bump the browser
never refetches sw.js and the old worker keeps running.

Unrelated but confirmed while tracing this: /assets/images/themes/arctic-ice.png
is requested by the browser and 404s, but that string exists nowhere in the
code, the database or the build. It was a stale reference served out of this
same cache, not a missing asset.

src/components/pwa-register.tsx

@@ -2,7 +2,10 @@
 
 import { useEffect } from "react";
 
-const SW_VERSION = "3";
+// Must move together with the caches in public/sw.js. It is part of the
+// registration URL, so an unchanged value means the browser never refetches
+// sw.js and keeps running the previous worker.
+const SW_VERSION = "4";
 
 export function PwaRegister() {
 	useEffect(() => {