Update docs logos to new blockier format

[GeorgePearse]

Summary

Update the documentation site branding to use the newer, blockier logo format across all pages.

Scope

• Replace current logo assets used by MkDocs theme/header
• Ensure light/dark variants are correct
• Update any inline logo references in docs pages (markdown/images)
• Update favicon/app icons if applicable

Likely Locations

• docs/assets/
• resources/
• mkdocs.yml (theme/logo settings)

Acceptance Criteria

• New logo appears in the docs header/nav
• Light/dark mode uses the correct variants
• No stale old logo assets referenced anywhere in docs/
• Site builds without broken image links