feat: Implement an Admin token sweep function for accidental transfers

[AlAfiz]

Description

Users frequently make the mistake of sending tokens directly to the smart contract address instead of using the proper swap function.
Because our contract doesn't have a way to access un-tracked balances, those tokens are permanently locked.
We need a sweep_tokens function that allows the Admin to rescue these accidentally transferred funds and return them to the users.
This function must explicitly calculate the difference between the pool's mathematical reserves and the actual contract balance.

Requirements

• Create a sweep_tokens(token: Address, to: Address) function restricted to the Admin.
• Read the mathematical reserve of the requested token from the pool state.
• Read the actual Soroban token.balance() of the contract.
• Allow the Admin to transfer the difference (actual_balance - reserve) to the specified recovery address.