Enhance main display by making the central card more see-through

Adjusted card opacity and overlay darkness to highlight the background video.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 239404e1-aadb-4dd2-b8fb-ea05070af453
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/a3a4d2b6-5525-45e1-8bce-dbe37a513c07/a6f69407-9466-42fb-b5a8-8b294228eef3.jpg
