Create comprehensive DTOs and validation schemas

[RUKAYAT-CODER]

Clear DTOs and validation improve safety.

Acceptance Criteria:

• All endpoints have DTOs
• Validation decorators used
• Documentation in DTO comments
• Tests for all validations

[Truphile]

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

Let's fix this you know I can deliver.

Thanks

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

[opepraise]

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

I can work on this issue. Please, assign.

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

[drips-wave]

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

🧑‍💻 @Truphile: 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.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊