debug: verify WebP blob data integrity and URL lifecycle

components/converter/ConversionPreview.tsx

@@ -46,12 +46,17 @@ export function ConversionPreview({ job, onDownload }: ConversionPreviewProps) {
   // Create preview URL for result
   React.useEffect(() => {
     if (job.result && job.status === 'completed') {
+      console.log('[Preview] Creating object URL for blob');
       const url = URL.createObjectURL(job.result);
       setPreviewUrl(url);
+      console.log('[Preview] Object URL created:', url);
 
       return () => {
+        console.log('[Preview] Revoking object URL:', url);
         URL.revokeObjectURL(url);
       };
+    } else {
+      setPreviewUrl(null);
     }
   }, [job.result, job.status]);