[Backend] Introduce platform-wide request validation contracts

[Solomonsolomonsolomon]

Replace manual body/query checks with structured reusable validation and standardized error responses across public and internal APIs. This should become the foundation for more accurate docs and safer integrations.nn- Priority: Mediumn- Area: API / Validationn- Advanced Scope: validation architecture, API contracts, error standardization

[Jumongweb]

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

Hi maintainer, i will like to solve this issue

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[Zainab5970]

@Zainab5970 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

please can i work on the issue

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[drips-wave]

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

🧑‍💻 @middalukawunti-lang: 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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[NickiM84]

@Solomonsolomonsolomon please help me and close the issues, I forgot to close it on the PR.

[priyankbhikadiya]

@priyankbhikadiya has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I'd like to work on this issue because it's a great opportunity to contribute to the project while improving the user experience. I have experience with JavaScript, Node.js, Python, and frontend development, and I'm comfortable working with Git/GitHub and following existing project standards to deliver a clean implementation.

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[drips-wave]

Congratulations, @priyankbhikadiya! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @priyankbhikadiya: 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 🌊