[Contract] Add Reentrancy Protection Guards Across All Payment Stream Functions

[Idrhas]

Task Description

Integrate reentrancy guard decorators and state locks to all state-mutating functions in Soroban stream contracts.

Requirements & Scope

• Target Area: Soroban Rust Smart Contracts (contracts/ / src/contracts/)
• Key Objectives:
  1. Implement complete, production-ready Rust code following Soroban SDK best practices.
  2. Include explicit authorization checks (require_auth()) and error handling enums.
  3. Write comprehensive unit tests in Rust covering success, failure, and edge cases.
  4. Ensure storage TTL management and efficient state footprint.

Acceptance Criteria

• Code compiles cleanly with zero warnings (cargo build --target wasm32-unknown-unknown).
• All unit tests pass (cargo test).
• Proper error codes defined in Error enum.
• Complete documentation comments added to public functions.

[heymide]

@heymide has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

This issue aligns well with my experience. I can work on it and submit a polished PR for review.

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

[numdinkushi]

@numdinkushi has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi, I would like to work on this issue

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

[drips-wave]

Congratulations, @numdinkushi! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @numdinkushi: 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 🌊