feat: Add the frontend support for MFA (#12372)

FE support for https://github.com/chatwoot/chatwoot/pull/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: iamsivin <iamsivin@gmail.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/views/layouts/vueapp.html.erb

@@ -44,6 +44,7 @@
         whatsappApiVersion: '<%= @global_config['WHATSAPP_API_VERSION'] %>',
         signupEnabled: '<%= @global_config['ENABLE_ACCOUNT_SIGNUP'] %>',
         isEnterprise: '<%= @global_config['IS_ENTERPRISE'] %>',
+        isMfaEnabled: '<%= Chatwoot.mfa_enabled? %>',
         <% if @global_config['IS_ENTERPRISE'] %>
         enterprisePlanName: '<%= @global_config['INSTALLATION_PRICING_PLAN'] %>',
         <% end %>