[Feature] Secure PIN to unlock settings

[dmnyc]

Feature Description

Secure critical settings behind a user-defined PIN to protect the POS owner from someone tampering with the address or settings when they are not looking.

Problem It Solves

In the case where an employee is using the POS when the owner of the business/wallet is not present, we should have a way to prevent someone from maliciously changing the Lightning Address, or resetting the POS to intercept payments from customers.

Additional Context

This would need to be saved in local storage. It's not a completely foolproof method, but it should be sufficiently secure in most use cases.