Improve media loading performance and user experience

Add `loading="lazy"` attribute to image elements in MediaUpload component for improved performance.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/fGL9Pd7

client/src/components/media-upload.tsx

@@ -223,6 +223,7 @@ export default function MediaUpload() {
                           src={media.facebookFeedUrl || media.originalUrl} 
                           alt={media.fileName}
                           className="w-full h-full object-cover"
+                          loading="lazy"
                         />
                       )}
                       <div className="absolute top-2 right-2 flex gap-2">