Fix Multilanguage Settings Issue in CodeIgniter Admin Panel

We are experiencing a problem where changes to the language settings in the admin panel (like default language, system language, and Google Translate options) are not being saved or applied properly. This affects both the frontend and backend multilingual behavior.

We need a skilled CodeIgniter developer to investigate and fix this issue thoroughly.

Scope of Work.

- Investigate why language settings are not being saved/applied correctly.
- Review and debug the full flow:
- Form submission (`POST` data)
- Controller function (`add_extra_config`)
- Related model method(s)
- Session updates (`site_lang`)
- Affected language JSON or PHP files
- Fix any broken logic in the controller, model, or views.
- Ensure `languages[]`, `glanguage[]`, and related settings are correctly saved in the `user_settings` table and reflected in the app.
- Validate that selected language loads correctly across user/admin panels.
- Clean up the frontend/backend if needed:
- Fix missing or invalid language files/keys
- Ensure fallback/default languages work as expected
- Optional but appreciated: Add feedback messages or error handling.

Tech Stack:
- CodeIgniter 3 (PHP)
- Bootstrap & jQuery (admin panel UI)

What We Expect:

- Clean and tested fix
- Code is readable and maintainable
- A quick summary of the changes made

Required Skills:
- CodeIgniter 3 expertise
- Strong debugging skills in PHP
- Familiarity with multilingual setups (language switching, sessions, translations)