Rename `config.php` to `app.php` and move 2FA configs

[armanist]

We need to rename the existing config.php file to app.php for better clarity and separation of concerns.
Additionally, the following authentication-related configurations should be moved from app.php to auth.php.

Changes Required

1. Rename file:

   • From: config/config.php
   • To: config/app.php

2. Move these configuration keys from: app.php to: auth.php

'two_fa' => env('TWO_FA', true),
'otp_expires' => 2,

3. Update all references in the codebase and tests