🔐 1. PIN Hashing for Enhanced Security

• PINs are now securely stored as SHA-256 hashes instead of plain text.

• The raw PIN is never exposed to the client after being saved.

• Client-side unlock uses hash comparison (sha256(inputPIN) === storedHash), improving the privacy and safety of user credentials.

⏱ 2. Improved Auto-Lock Stability

• Auto-lock and inactivity timer now persist across page refreshes using sessionStorage.

• Ensures the lock screen reappears even if the user reloads the browser tab.