This PR introduces Transferable Allocations, allowing team members or investors to trade their unvested positions Over-The-Counter (OTC) by transferring vault ownership. This is a critical feature for DeFi liquidity, controlled strictly by administrative configuration to prevent unauthorized secondary markets.

🎯 Key Changes
Vault Configuration: Added an is_transferable boolean to the VaultConfig struct.

Transfer Logic: Implemented the transfer_vault function which updates the beneficiary address of a specific vault ID.

Access Control: * Ensures only the current beneficiary (owner) can initiate a transfer.

Verifies that the vault has been explicitly marked as transferable by the Admin.

Safety Guards: Added a "Non-transferable" revert string to satisfy the compliance requirement.

💻 Implementation Snippet (Soroban/Rust)
The core logic ensures that transferability is an opt-in security feature:

Rust
pub fn transfer_vault(env: Env, vault_id: u64, new_beneficiary: Address) {
let mut vault = get_vault(&env, vault_id);

// Verify current ownership
vault.beneficiary.require_auth();

// Check if the Admin enabled secondary transfers for this vault
if !vault.is_transferable {
    panic!("Vault is non-transferable");
}

// Update ownership
vault.beneficiary = new_beneficiary;
put_vault(&env, vault_id, vault);

}
✅ Acceptance Criteria Checklist
[x] State Update: is_transferable flag added to vault storage.

[x] Transfer Function: transfer_vault(vault_id, new_beneficiary) successfully updates the ledger.

[x] Constraint Validation: Reverts with "Vault is non-transferable" if the flag is set to false.

[x] Auth Check: Verified that only the current owner can move their allocation.

🚀 How to Test
Initialize a Vault: Set is_transferable: true.

Execute Transfer: Call transfer_vault from the current beneficiary's wallet.

Validate Failure: Attempt to transfer a vault where is_transferable: false and verify the panic message.

🔗 Linked Issues
Closes #24
Closes #45