fix: stabilize pro checkout loading

frontend/public/sw.js

@@ -1,5 +1,14 @@
-const CACHE_NAME = "polyweather-v1";
-const STATIC_ASSETS = ["/_next/", "/favicon"];
+const CACHE_NAME = "polyweather-v2";
+const CACHEABLE_PUBLIC_ASSETS = [
+  "/favicon.ico",
+  "/favicon-16x16.png",
+  "/favicon-32x32.png",
+  "/apple-touch-icon.png",
+  "/android-chrome-192x192.png",
+  "/android-chrome-512x512.png",
+  "/manifest.webmanifest",
+  "/site.webmanifest",
+];
 
 self.addEventListener("install", (event) => {
   event.waitUntil(self.skipWaiting());
@@ -7,18 +16,27 @@ self.addEventListener("install", (event) => {
 
 self.addEventListener("activate", (event) => {
   event.waitUntil(
-    caches.keys().then((keys) =>
-      Promise.all(
-        keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key)),
-      ),
-    ),
+    caches
+      .keys()
+      .then((keys) =>
+        Promise.all(
+          keys
+            .filter((key) => key !== CACHE_NAME)
+            .map((key) => caches.delete(key)),
+        ),
+      )
+      .then(() => self.clients.claim()),
   );
 });
 
 self.addEventListener("fetch", (event) => {
   const url = new URL(event.request.url);
 
-  if (STATIC_ASSETS.some((prefix) => url.pathname.startsWith(prefix))) {
+  // Do not cache-first Next.js build chunks. A user can keep an old app shell
+  // open across deployments; if checkout UI is loaded later, stale/missing
+  // chunks surface as a generic page fault. Let the browser/Vercel handle
+  // immutable _next/static asset caching instead.
+  if (CACHEABLE_PUBLIC_ASSETS.includes(url.pathname)) {
     event.respondWith(
       caches.open(CACHE_NAME).then((cache) =>
         cache.match(event.request).then(