- Add preloadMedia() for async image/video loading before display
- Implement renderLoadingSkeleton() with fa-circle-notch fa-spin animation
- Add fadeIn transition (opacity 0→1) for main media elements
- Remove shimmer gradient animation from thumbnails for cleaner look
- Use solid background color placeholder with subtle fade-in for thumbnails
- Fixes progressive rendering of remote images from top to bottom
- Prevents black flash during loading with proper loading states