[Feature] Optional Biometric WebAuthn (TouchID/FaceID) Support

[BrianV1981]

Summary

Add optional support for the Web Authentication API (WebAuthn/FIDO2) to allow users to authenticate using biometric hardware (TouchID on Mac/iOS, FaceID, Windows Hello, or YubiKeys).

Implementation Details

• Provide an 'Enable Biometrics' toggle in the settings.
• When enabled, the browser registers the device's secure enclave as a passkey.
• During the login flow, instead of entering the Admin Password, the user can use their biometric prompt.
• This should be strictly OPTIONAL and act as a replacement/shortcut for the password factor, while keeping the TOTP and Stealth Passphrase intact for ultimate security.