feat: Update CockroachDB logo for better visibility

[viragtripathi]

Summary

This PR updates the CockroachDB logo in the UI to improve visibility and consistency with other database logos.

Changes

• Replaced small PNG logo with high-quality SVG (base64-encoded data URI)
• Added linting exception for the long data URI line
• Logo now displays at appropriate size and stands out like other database logos

Testing

• Verified logo displays correctly in Streamlit UI at http://localhost:8501
• Confirmed logo size is appropriate and matches visual weight of other database logos

Related

Follows up on previous CockroachDB integration work (PRs #630, #647, #655)

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: viragtripathi
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[viragtripathi]

/assign @XuanYang-cn