Add user and page access management, fetch user on first load, and link user data

• Add Dietela cover loading state on initial page.

• Add page access management of the following pages:

Initial page & Registration page:

• paid or user is nutritionist/admin -> navigate to profile
• unpaid client -> navigate to checkout Login page (accessed from link from initial page):
• haven't done questionnaire -> navigate to dietela quiz
• haven't select program and nutritionist -> navigate to choose plan
• when authenticated, same logic as initial page

• Handle better loading states to all pages.
• Fetch user API on first load.
• Link user data on signup and google login. (Google login might need a different logic, but its okay for now)