Support Autofill for Concatenated OTP Authentication (Password + OTP)

[ddjain]

###Description

Some authentication systems use concatenated OTP authentication, where the OTP is appended directly to the password in the same input field during login.

This workflow is used in systems like

• FreeIPA
• Keycloak (with certain configurations)
• Duo Security
• PrivacyIDEA

Why systems do this

• Works with legacy login forms that only support one password field
• Easier integration with PAM / LDAP

Currently, the authenticator extension generates OTP but does not assist with appending it to the password. Supporting this (e.g., append OTP to password or provide quick copy of password+OTP) would reduce manual errors, speed up login, and improve usability for environments that rely on concatenated OTP authentication.