feat: threshold management

[emmanuelJet]

Feature Description

Implement functionality to manage the signatory threshold, which determines the minimum number of signers required to approve transactions and certain administrative changes.

Acceptance Criteria

• Owner can update the signatory threshold under specified conditions.
• Increasing the threshold when total signers are equal to or greater than the current threshold requires signers' approvals.
• Threshold changes are enforced correctly in the contract logic.
• Transactions cannot proceed if total signers are less than the required threshold.