BE - Implement all related passkey controller & concerns

Context

Backend for the passkeys controller and connect it to the existing infrastructure

Implementation Plan

• Create passkey controller actions
• Connect it to the sessions controller
• Connect it to the two_factor_auths controller
• Update any /concerns to create 2FA parity per our UX flow
  • For Phase 1, it means that passkeys can only be used as a 2FA method if at least 1 OTP/second_factor_webauthn_registration is enabled
• Add specs