feat/add-passkey-login-registration

[RumanCodes]

Description

This PR adds Passkey (WebAuthn) authentication support as a new independent provider in FluentAuth, enabling passwordless login and registration using device-based authentication (biometrics/PIN).

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Changes

Passkey System

• Implemented WebAuthn-based registration and login flow
• Added support for multi-device passkey management

Backend

• Added PasskeyHandler for AJAX endpoints, shortcode, and asset loading
• Added PasskeyService for:
  • Challenge generation
  • WebAuthn verification
  • RP/origin validation
  • Public key handling
• Added PasskeyCredentialRepository
• Introduced fls_passkey_credentials table

Settings

• Enable Passkey Login
• Show passkey login button on login forms
• Passkey user verification option

Frontend

• Added passkey.js
• Integrated WebAuthn API (create / get)
• Added Mix build entry for compiled asset

UI

• Added [fluent_auth_passkeys] shortcode for managing passkeys

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Security

• RP and origin validation
• Challenge-based authentication
• Public key verification
• Replay attack protection via sign counter

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Testing

• Registration & login flow
• Multi-device support
• Credential deletion
• Chrome & Safari tested

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