feat: MFA (#12290)

## Linear:
- https://github.com/chatwoot/chatwoot/issues/486

## Description
This PR implements Multi-Factor Authentication (MFA) support for user
accounts, enhancing security by requiring a second form of verification
during login. The feature adds TOTP (Time-based One-Time Password)
authentication with QR code generation and backup codes for account
recovery.

## Type of change

- [ ] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

- Added comprehensive RSpec tests for MFA controller functionality
- Tested MFA setup flow with QR code generation
- Verified OTP validation and backup code generation
- Tested login flow with MFA enabled/disabled

## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/controllers/api/v1/profile/mfa_controller.rb

@@ -0,0 +1,68 @@
+class Api::V1::Profile::MfaController < Api::BaseController
+  before_action :check_mfa_feature_available
+  before_action :check_mfa_enabled, only: [:destroy, :backup_codes]
+  before_action :check_mfa_disabled, only: [:create, :verify]
+  before_action :validate_otp, only: [:verify, :backup_codes, :destroy]
+  before_action :validate_password, only: [:destroy]
+
+  def show; end
+
+  def create
+    mfa_service.enable_two_factor!
+  end
+
+  def verify
+    @backup_codes = mfa_service.verify_and_activate!
+  end
+
+  def destroy
+    mfa_service.disable_two_factor!
+  end
+
+  def backup_codes
+    @backup_codes = mfa_service.generate_backup_codes!
+  end
+
+  private
+
+  def mfa_service
+    @mfa_service ||= Mfa::ManagementService.new(user: current_user)
+  end
+
+  def check_mfa_enabled
+    render_could_not_create_error(I18n.t('errors.mfa.not_enabled')) unless current_user.mfa_enabled?
+  end
+
+  def check_mfa_feature_available
+    return if Chatwoot.mfa_enabled?
+
+    render json: {
+      error: I18n.t('errors.mfa.feature_unavailable')
+    }, status: :forbidden
+  end
+
+  def check_mfa_disabled
+    render_could_not_create_error(I18n.t('errors.mfa.already_enabled')) if current_user.mfa_enabled?
+  end
+
+  def validate_otp
+    authenticated = Mfa::AuthenticationService.new(
+      user: current_user,
+      otp_code: mfa_params[:otp_code]
+    ).authenticate
+
+    return if authenticated
+
+    render_could_not_create_error(I18n.t('errors.mfa.invalid_code'))
+  end
+
+  def validate_password
+    return if current_user.valid_password?(mfa_params[:password])
+
+    render_could_not_create_error(I18n.t('errors.mfa.invalid_credentials'))
+  end
+
+  def mfa_params
+    params.permit(:otp_code, :password)
+  end
+end