[Contract] Rework `multi_hop_swap` into a realistic path execution contract

[Solomonsolomonsolomon]

Replace simplistic reserve and price assumptions with safer routing abstractions, slippage invariants, and explicit downstream pool integration expectations.

[alexatsejames-alt]

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

Hi can you please assign these issue to me

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

[Stephan-Thomas]

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

hi, i would like to work on this.

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[Jessepriase]

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

i would like to work on this issue

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[drips-wave]

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

🧑‍💻 @Jessepriase: 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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🌊 Happy Wave 🌊

[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @Jessepriase as part of the Stellar Wave Program's 5th Wave 🥳

Moderator's reason: [Auto-assessed] PR #404 was merged and successfully reworks the multi-hop swap contract with realistic routing, slippage invariants, and a pool interface as requested in the issue. The contributor was assigned to the issue, provided comprehensive tests, and no maintainer objections were recorded.

😎 @Jessepriase: 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.

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

ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.