Add swapAssets function

[MissBlue00]

Task

Add a swapAssets function to perform atomic asset swaps on Stellar.

Details

• Function signature: swapAssets(params: SwapParams): Promise<SwapResult>
• Support swapping between any two Stellar assets
• Use path payment or atomic swap patterns
• Handle liquidity and price considerations
• Add SwapParams and SwapResult interfaces

Test

Run pnpm --filter @stellar-pay/payments-engine build to verify no TypeScript errors.

[akinboyewaSamson]

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

Hi! I’m a full-stack developer with a strong blockchain background. I’d love to handle this issue and can deliver a clean, reliable solution. Kindly assign it to me.

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