[Feature] Flash Loan Implementation with 0.05% Fee Model

[AlAfiz]

Description: Introduce flash loan capabilities to the TradeFlow liquidity pools. Users should be able to borrow arbitrary amounts of an asset in a single transaction, provided the borrowed amount plus a 0.05% protocol fee is returned by the end of the invocation.
Context / Motivation: Flash loans increase capital efficiency, empower arbitrageurs to keep TradeFlow prices aligned with the broader Stellar ecosystem, and generate additional passive yield for our Liquidity Providers.
Acceptance Criteria: - [ ] Create a flash_loan function that accepts a receiver contract address, asset, and amount.

• Utilize a cross-contract call to the receiver's execute_operation function.
• Assert that the pool balance post-execution is initial_balance + fee.
• Implement reentrancy protection to prevent the receiver from draining the pool during the callback.
  Technical Pointers: Leverage Soroban's temporary storage for the reentrancy guard. The receiver contract must implement a specific interface trait to handle the callback; define this interface clearly in the project's interfaces/ module.

[grantfox-oss]

🦊 GrantFox — @Menjay7 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #172)
2. Your PR will be reviewed by the BETAIL-BOYS maintainers

Good luck! Track your progress on GrantFox.