[CT-22] Implement contract admin transfer mechanism in assetsup in opsce crate

[yusuftomilola]

Problem

The assetsup contract sets an admin address at initialization but provides no way to transfer admin rights to a new address. If the admin key is compromised, the contract is permanently stuck with the compromised admin.

Proposed Solution

Create contracts/opsce/src/admin_transfer.rs. Implement a two-step admin transfer: the current admin proposes a new admin, and the new admin must accept.

Acceptance Criteria

• propose_admin_transfer(env, new_admin) stores the pending admin (current admin only)
• accept_admin_transfer(env) — caller must match the pending admin stored in step 1
• cancel_admin_transfer(env) removes the pending admin (current admin only)
• get_pending_admin(env) returns the address awaiting acceptance, or None
• Emits admin_transfer_proposed and admin_transfer_completed events
• Unit tests cover: full happy path, non-admin propose fails, wrong address accept fails, cancel and re-propose

[supreme2580]

@supreme2580 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi can I be assigned to this issue

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[nafiuishaaq]

@nafiuishaaq has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Let me professionally implement this task as soon as possible with an ETA of 2 to 4 hours

ℹ️ Repo Maintainers: To accept this application, review their application or assign @nafiuishaaq to this issue.

[drips-wave]

Congratulations, @nafiuishaaq! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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