chore: Upgrade soroban-sdk from 21.7.0 to latest stable

[Haroldwonder]

Track the latest Soroban SDK release and update dependencies, fixing any breaking API changes.

[Jonniie]

@Jonniie has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

Hi there, can I work on this please

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

[Macnelson9]

@Macnelson9 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

Hello Maintainer,

I’m a smart contract and full-stack developer interested in contributing to this issue. I have hands-on experience with Rust, Soroban, Cairo, and TypeScript, and I’ve contributed to similar projects in the past.

I focus on building secure, scalable blockchain solutions with clean and maintainable code. Based on the scope of this issue, I’m confident I can deliver a complete solution within 24 hours of assignment.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Macnelson9 to this issue.

[drips-wave]

Congratulations, @Macnelson9! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @Macnelson9: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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🌊 Happy Wave 🌊

[drips-wave]

This issue has been completed by @Macnelson9 as part of the Stellar Wave Program's 4th Wave 🥳

😎 @Macnelson9: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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