feat(lending): Support multi-collateral positions (basket collateral)

[nanaf6203-bit]

Allow a single borrower position to be backed by N collateral assets with weighted health-factor calculation. Reference contracts/lending/README.md for design constraints.

[emmyokolo2525-cyber]

@emmyokolo2525-cyber has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi Maintainer,

I'd love to work on this issue. I can implement a clean and accessible dark mode experience with persistent theme preferences while ensuring consistent styling across the application.

Thank you for your considerations

ℹ️ Repo Maintainers: To accept this application, review their application or assign @emmyokolo2525-cyber to this issue.

[Spycall]

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

Hi Team can i work on this

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

[drips-wave]

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

🧑‍💻 @Spycall: 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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