docs: notice temporary pause of MEV Auction infrastructure

[adnpark]

✨ Proposed Changes

• Add a suspension notice of MEV Auction infra

🗂️ Types of changes

• Minor Issues and Typos
• Major Content Contribution
• Others (e.g. platform-specific changes)

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✅ Checklist

• I have read the CONTRIBUTING GUIDELINES.
• If following Standard Workflow: I have linked the approved issue below.
• If submitting without a prior issue (Maintainer/Regular): I have provided detailed context in the "Proposed Changes" section above.
• My changes render correctly (if applicable, run npm run build locally).
• [] I have added necessary documentation updates (if appropriate).
• Any dependent changes have been merged and published.

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💡 Further comments