docs: refresh bilingual README and demos

[Eco1i]

Summary

• Refresh the English README and add a Chinese README with language switching.
• Update public screenshots using synthetic demo data.
• Add localized 10-second GIF demos for English and Chinese README pages.

Validation

• git diff --check
• GIFs verified at 40 frames / 10 seconds each.
• No production data or local paths included in the published assets.