docs: propose OP backoffice direction

[wlds]

Summary

• Add an OP backoffice design proposal.
• Position OP as an operations workflow layer on top of the existing admin console.
• Outline MVP scope, backend/frontend direction, RBAC, audit logs, and rollout order.

Test Plan

• git diff --check HEAD~1 HEAD

[github-actions]

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[wlds]

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[wlds]

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