Implement User Authentication

[caabernathy]

Description:
Develop the authentication system for Restill, enabling users to create accounts, log in, and optionally maintain anonymity. Refer to the Figma design.

Requirements:

1. Set up user registration and login functionality.
2. Integrate third-party authentication library (e.g., Clerk, Firebase).
3. Allow users to toggle anonymity during account creation or profile updates.
4. Ensure data security and compliance with best practices.

Deliverables:

• Functional login and registration screens.
• Backend API endpoints for user management.
• Documentation for the authentication flow.