Add creator list cursor response serializer

[Chucks1093]

Summary

Add a serializer dedicated to creator list cursor metadata.

Acceptance Criteria

• serializer keeps cursor metadata shaping separate from route handlers
• output stays consistent across cursor-aware list responses
• helper is small and reusable

Contributor coordination: https://t.me/accesslayerorg

[kryputh]

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

pls asign to me thanks sir

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Congratulations, @kryputh! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on March 30, 2026.

🧑‍💻 @kryputh: 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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[drips-wave]

This issue has been completed by @kryputh as part of the Stellar Wave Program's 3rd Wave 🥳

😎 @kryputh: 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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