Add creator feed cursor decode helper with validation

[Chucks1093]

Summary
Add creator feed cursor decode helper with validation

Scope

• add helper to decode/validate creator feed cursors in one place\n- return consistent parse errors for invalid cursor formats\n- apply helper in creator feed endpoint path

Acceptance Criteria

• scoped change is implemented with no unrelated file churn
• docs/tests are updated where applicable
• contributor can validate the outcome locally

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[The-Big-Danny]

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

I'd like to claim this issue.

​ETA: Draft PR ready in [4Hours].

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[Yash-Karakoti]

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

i can work on this , kindly assign !!

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[eischideraa-unn]

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

Hi, maintainer. I would like to work on this issue.

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[Johnsmichael150]

@Johnsmichael150 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I would like to work on this issue

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Congratulations, @Johnsmichael150! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

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[drips-wave]

This issue has been completed by @Johnsmichael150 as part of the Stellar Wave Program's 4th Wave 🥳

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