docs(contract): NatSpec-style documentation for all public functions

[Idrhas]

Add comprehensive inline documentation to every public contract function describing params, return values, errors, and events.

[Vivian-04]

@Vivian-04 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hiiiiii, I would love to work on this asap for youuuu
Kindly assign this to meeee!

ETA: 2-3hours

Looking forward to working with youuuu!
Thank youuu!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Vivian-04 to this issue.

[sadiqabubakar826-del]

@sadiqabubakar826-del has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer am active to resolve this issue, have gone through it and will carry out the task perfectly and diligently
Kindly assign this to me thanks

ℹ️ Repo Maintainers: To accept this application, review their application or assign @sadiqabubakar826-del to this issue.

[drips-wave]

Congratulations, @Vivian-04! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Vivian-04: 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 🌊