feat: add ITreasuryModule interface for treasury modules

[Cybermaxi7]

Description

This PR adds a standard interface for treasury modules, enabling consistent interaction between governance and treasury modules in the protocol.

Changes Made

• Created contract/src/ITreasuryModule.cairo interface file.
• Defined function signatures for:
  • execute_transfer(token_address, recipient, amount)
  • set_governance_module(new_governance_module)
  • get_balance(token_address) -> u256
• Added Cairo-style docstrings for clarity and maintainability.

Checklist

• I have tested my changes locally.
• I have updated the documentation (if applicable).
• I have added/updated unit tests (if applicable).
• My code follows the project's coding standards.
• My changes do not introduce new warnings or errors.

Related Issues

• Fixes Define the ITreasuryModule Interface #88

Screenshots or Screen Recording

N/A

Additional Context

This interface will help future governance modules integrate seamlessly with any compliant treasury module and improve protocol modularity.

[Cybermaxi7]

@bitfalt i am waiting for a review

[bitfalt]

looks like CairoZero, we don't use that anymore.

[Cybermaxi7]

@bitfalt i have made the necessary changes
thank you