fix: resolve pre-cache 404s and implement Bunker v7 with SWR

src/app/layout.tsx

@@ -19,7 +19,7 @@ export const metadata: Metadata = {
         template: "%s | Whisky Vault"
     },
     description: "Dein persönlicher Whisky-Begleiter zum Scannen und Verkosten.",
-    manifest: "/manifest.json",
+    manifest: "/manifest.webmanifest",
     appleWebApp: {
         capable: true,
         statusBarStyle: "default",

src/components/UploadQueue.tsx

@@ -127,8 +127,10 @@ export default function UploadQueue() {
 
     useEffect(() => {
         const handleOnline = () => {
-            console.log('Online! Triggering background sync...');
-            syncQueue();
+            console.log('Online! Waiting 2s for network stability...');
+            setTimeout(() => {
+                syncQueue();
+            }, 2000);
         };
 
         window.addEventListener('online', handleOnline);