fix: reject zero address in owner and transfer fields (#140)

[edehvictor]

Overview

This PR addresses Issue #140 by implementing simulated "Zero Address" rejection. It explicitly checks for the Stellar null address (GAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAWHF) and prevents it from being used as an owner or transfer recipient.

Changes Made

commitment_core

• Added is_zero_address helper function.
• Updated create_commitment to reject zero addresses as the owner.
• Added ZeroAddress variant to the CommitmentError enum.
• Added test_create_commitment_zero_address_fails unit test.

commitment_nft

• Added is_zero_address helper function.
• Updated mint function to reject zero addresses as the owner.
• Updated transfer function to reject zero addresses as the recipient (to).
• Added test_mint_to_zero_address_fails and test_transfer_to_zero_address_fails unit tests using should_panic with the TransferToZeroAddress (error code 18).

Closes #140

[edehvictor]

@1nonlypiece, please review and merge

[1nonlypiece]

@edehvictor resolve the conflicts

[edehvictor]

Fix the compile error

[edehvictor]

fix is_zero_address function error

[edehvictor]

Fix the compile error

[edehvictor]

Fix compile error

[edehvictor]

fixing the compile error

[edehvictor]

fixing the compile error

[edehvictor]

fixed error

[edehvictor]

fix error

[edehvictor]

fix test.rs file

[1nonlypiece]

@edehvictor resolve the conflicts & fix the pipeline

[1nonlypiece]

@edehvictor

[edehvictor]

@1nonlypiece, I have merge conflict. kindly review

[1nonlypiece]

please resolve the conflicts

[edehvictor]

Gm @1nonlypiece, I have resolved conflict. Kindly merge

[edehvictor]

@1nonlypiece, please kindly review. We're less than two hours to the end of Wave 2

I have resolved conflict