[sebenns]

Summary

• Replace the previous nigiri logo with a clean geometric version of the supplied Sushi crest for the small navigation logo.
• Provide light and dark variants and matching favicons.
• Preserve the supplied worn SVG unchanged as a separate branding asset.

Verification

• Playground production build passed.
• Repository formatting and diff checks passed.
• All SVG files parsed successfully; the worn asset matches the original byte for byte.
• Checked sidebar logo loading and appearance in light and dark themes, favicon resources, and mobile navigation in the built Playground.