Description:
Instead of just a boolean is_transferable flag, wrap the vesting position into a standard Soroban Non-Fungible Token (NFT). Whoever holds the NFT in their wallet has the right to call claim() and receive the vested tokens.
Acceptance Criteria:
[ ] Implement the Soroban NFT standard interfaces within the vault contract.
[ ] Mint an NFT with a unique token_id matching the vault_id upon creation.
[ ] Ensure claim() strictly pays out to the current owner of the NFT.
Labels: feature, interoperability