Implement Partial Locker Approval for Withdrawals

[Lomet]

Description
Currently, the contract requires either the owner's signature or approval from all lockers to authorize a withdrawal. This needs to be changed to support M-of-N approval, where a subset of lockers (e.g., 2 out of 3 or 3 out of 5) can authorize withdrawals without requiring unanimous consent.

Acceptance Criteria
✅ Allow withdrawals if at least M out of N lockers approve.
✅ Keep existing functionality where the owner’s signature alone can approve.
✅ Ensure security: Attackers should not be able to bypass the required quorum.

Proposed Solution
Introduce a threshold (M) parameter when opening a safe.
Modify _validateOpenData to check if M out of N lockers have signed.
Use an efficient counting mechanism to verify M valid approvals.
Example Cases
3 out of 5 lockers approve → Withdrawal allowed ✅
2 out of 5 lockers approve → Withdrawal denied ❌ (if M=3)
Owner signs → Withdrawal allowed (no lockers needed) ✅
No owner, but all M required lockers approve → Withdrawal allowed ✅