📸 Add bilingual sample social cards

- English sample card (claude-code-session-sharing-card-en.png)
- Chinese sample card (claude-code-session-sharing-card-zh.png)
- Showcase the new Vercel-inspired design
- Demonstrate typography and layout improvements

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: binggg