Admin page and username availability check
Long time no see) So I added username availability check every 1500 ms, and admin page, where admin can view users and delete them. Frontend should be improved bc it doesnt utilize /admin/view_users full potential, but it is good for now. Also as you can see i added roles, so now you can have admin or user role, where admin role users have access to this page.
Added enspoints:

GET /api/users/check -> Check if a username exists
GET /admin -> Admin dashboard
GET /admin/view_users -> List users (by page)
DELETE /delete_user/<id> -> Delete a user