Add flash loan attack prevention with price manipulation detection

[Smartdevs17]

Description

Flash loans can be used for price manipulation attacks. Implement detection and prevention mechanisms including TWAP usage and sandwich attack mitigation.

Acceptance Criteria

• TWAP-based pricing during flash loans
• Flash loan amount limits relative to pool liquidity
• Price impact calculation and revert on excessive impact
• Concurrent flash loan detection
• MEV protection for liquidation pricing
• Attack simulation in test suite

Technical Scope

• stellar-lend/contracts/lending/src/flash_loan.rs
• stellar-lend/contracts/lending/src/mev_protection.rs
• stellar-lend/contracts/hello-world/src/flash_loan.rs
• stellar-lend/contracts/hello-world/src/mev_protection.rs
• Edge: oracle manipulation via flash loans, multi-block MEV attacks

[TUPM96]

Implemented this in PR #401: #401

Coverage added:

• configurable flash-loan loan/liquidity, price-impact, and TWAP-deviation guards
• per-asset active flash-loan detection
• liquidation pricing blocked while either liquidation asset is in an active flash-loan window
• tests for liquidity caps, excessive impact, and TWAP liquidity manipulation

[akintewe]

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

I'm a full-stack developer with 4+ years of experience building complex forms and e-commerce systems. I've previously worked on this project in the past as well as also developed inventory management systems for agricultural businesses and am well-versed in handling image processing and state management at scale.
I would love to work on this issue, my ETA is 1 hour.

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

[drips-wave]

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

🧑‍💻 @akintewe: 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 🌊

[drips-wave]

This issue has been completed by @akintewe as part of the Stellar Wave Program's 5th Wave 🥳

😎 @akintewe: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.