feat: refactor TwoFactorsAuthPlugin by modularizing passkey and TOTP functionalities

- Moved passkey-related functions to a new file: passkeys.ts
- Moved TOTP-related functions to a new file: totp.ts
- Created mfa-grace.ts for handling MFA grace period logic
- Introduced config-validation.ts for validating plugin configuration
- Updated TwoFactorsAuthPlugin to utilize the new modular functions
- Improved error handling and validation for passkeys and TOTP processes

Author: NoOne7135