Create and configure repos social-media-preview 'repo card'

[ClaudiuSchuster]

Create & Upload/Configure an image to customize the repository’s social media preview.

The image should be 1280×640px for best display.

See also attached template for reference:

[ClaudiuSchuster]

Completed:

• Add the PDrive repository social preview #40 added the 1280×640 social preview together with its reproducible, profile-based source workflow.
• The custom image is configured in the repository settings and was verified through the repository’s public Open Graph metadata.
• Show the social preview in the README #62 also surfaces the same card as the README hero.

Closing this as completed.