Prevent images from being cropped when displayed on social media

Update image display to use object-contain and remove server-side transformations, letting CSS handle aspect ratios.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/74fmQLN

client/src/components/media-upload.tsx

@@ -167,7 +167,7 @@ export default function MediaUpload() {
                     <img
                       src={selectedFile.facebookFeedUrl}
                       alt="Facebook preview"
-                      className="w-full h-full object-cover"
+                      className="w-full h-full object-contain bg-black"
                     />
                   ) : (
                     <div className="w-full h-full flex items-center justify-center">
@@ -191,7 +191,7 @@ export default function MediaUpload() {
                     <img
                       src={selectedFile.instagramFeedUrl}
                       alt="Instagram feed preview"
-                      className="w-full h-full object-cover"
+                      className="w-full h-full object-contain bg-black"
                     />
                   ) : (
                     <div className="w-full h-full flex items-center justify-center">
@@ -215,7 +215,7 @@ export default function MediaUpload() {
                     <img
                       src={selectedFile.instagramStoryUrl}
                       alt="Instagram story preview"
-                      className="w-full h-full object-cover"
+                      className="w-full h-full object-contain bg-black"
                     />
                   ) : (
                     <div className="w-full h-full flex items-center justify-center">