Updated POS files only.

How to apply:
1) Backup your current project.
2) Copy and replace these files into your Laravel project root.
3) Run:
   php artisan migrate
   php artisan optimize:clear
4) If you use public storage for logos/product images, ensure:
   php artisan storage:link

What was fixed:
- Missing controllers added for masters, purchases, returns, expenses, settings, barcodes
- AdminAuth login redirect fixed
- Dynamic CRUD for categories/brands/colors/sizes/units/suppliers
- Basic purchases, customer returns, supplier returns, expenses, settings pages made functional
- Settings persistence table added
- Conveyance bills schema compatibility migration added
- Barcodes page made functional
