Staking: Implement early withdrawal penalty

[LaGodxy]

Add penalty mechanism for early withdrawal from staking.

[munyanezaarmel]

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

I’m a full-stack engineer with experience building and integrating Soroban smart contracts with modern frontend applications. I’m comfortable working across both backend logic and UI layers, ensuring clean architecture, secure contract interactions, and smooth user experience. I write well-tested, maintainable code and communicate progress clearly throughout the development process. I can review the issue immediately and deliver a working solution within 24–48 hours. I’m confident I can resolve this efficiently and contribute high-quality improvements to the project.

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

[drips-wave]

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

🧑‍💻 @munyanezaarmel: 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 🌊