Issue 154: integration: Scaffold cross-contract calls to the native Stellar Asset Contract

[AlAfiz]

Description

Our dummy token interfaces are great for local testing, but on Mainnet, we have to interact with the official Stellar Asset Contract (SAC).
We need to update our token client initializations to explicitly use the token::Client provided by the Soroban SDK.
This ensures that when we call .transfer(), it natively moves real XLM or real USDC on the Stellar ledger.
This is the final bridge between our custom sandbox math and real-world ledger value.

Requirements

• Audit all token interactions in the contract (transfers, balance checks).
• Ensure we are importing and utilizing soroban_sdk::token::Client.
• Remove any mock or custom token interface traits we built during early prototyping.
• Document the SAC wrapping process for new assets in the protocol README.