Social preview image and org branding

[zeevdr]

Description

Create professional branding for the GitHub org and repos: logo, social preview image, org description.

Acceptance criteria

• Design a clean OpenDecree logo (simple, works at small sizes)
• Create social preview image (1280x640) for all repos
• Set org profile description and tagline
• Upload logo as org avatar
• Consider verifying a domain (opendecree.dev or similar) for the verified badge

Notes

• Social preview shows on link shares (Slack, Twitter, etc.) — high visibility for low effort
• Existing issue Social preview image #47 covers social preview for decree repo; this extends to org-level branding
• Keep branding minimal — a wordmark or simple icon