Update authentication to use Firebase Google

[BalajiRKB]

Summary:
Update the authentication system of the project to use Firebase Google as the authentication provider.

Background:
Currently, the project uses a different authentication mechanism. Migrating to Firebase Google authentication will enhance security and simplify user sign-in.

Tasks:

• Replace the existing authentication logic with Firebase Google authentication.
• Update all relevant backend and frontend code to support the new authentication flow.
• Update environment variables and configuration as needed.
• Test the new authentication system thoroughly.
• Update documentation to reflect the new authentication method.

Acceptance Criteria:

• Users can sign in and out using their Google accounts via Firebase.
• Old authentication methods are fully removed.
• Documentation is up-to-date.