Feature: Implement Google Authentication for Sign-in and Sign-up

[Dev1822]

Context & Goal
As a user, I want to be able to sign up and log in using my Google account so that I can access the platform quickly without needing to create and remember a new password. Implementing this will reduce friction during onboarding and improve conversion rates.

Acceptance Criteria

• Users can see a "Continue with Google" button on both the Sign-in and Sign-up pages.
• Clicking the button initiates the standard Google OAuth 2.0 flow.
• New Users: If a user authenticates with Google for the first time, a new account is automatically created in our database using their Google email, name, and profile picture.
• Existing Users: If a user with that email already exists, they are seamlessly logged in and linked to their existing account.
• Proper error handling is implemented (e.g., if the user cancels the Google auth flow or if there's a network issue), displaying user-friendly error messages.
• Authentication state is properly maintained (sessions/JWTs are issued just like email/password login).
• The implementation follows security best practices (e.g., state parameter for CSRF protection if applicable).

Technical Considerations

• Create and configure a new OAuth client in the Google Cloud Console.
• Set up the appropriate redirect URIs for development, staging, and production environments.
• Define necessary scopes (typically email and profile).
• Ensure the database schema can securely store the OAuth provider ID (e.g., google_id) and handle users who don't have a traditional password.

Dependencies

• Google Cloud Console Project setup (Requires Admin access).
• Secrets management: Need to securely store GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET in environment variables.

I would like to work on this issue if assigned