Deploy Smart Contract to Testnet for Backend Integration

[DeborahOlaboye]

Description

This PR deploys the smart contract to the stellar testnet.

Related Issues

Closes #32

Changes Made

• Renamed lock_rate → conversion_rate in conversion.rs
• Built and deployed the contract to Stellar testnet
• Included the bindings folder.
• Created a deployment/addresses.json file that includes contract address details for the deployed contract

How to Test

• Interact with the deployed testnet contract using the provided address in deployment/addresses.json.
• Verify that the renamed function behaves as expected.

Screenshots (if applicable)

Checklist

• My code follows the project's coding style.
• I have tested these changes locally.
• Documentation has been updated where necessary.

[portableDD]

Lgtm