Add Guest Mode Support

[VDuda]

Overview

This PR implements guest mode functionality, allowing users to interact with the application without requiring authentication. It includes a unified authentication system that handles both guest and authenticated users seamlessly.

Commits

• f7d63d2 - feat: implement guest mode support
• feb6dc3 - refactor: implement unified auth system for guest and clerk users

Key Changes

Authentication System

• Created custom useAuth hook to handle both guest and Clerk authentication
• Implemented unified auth utilities that work for both auth modes
• Prevented Clerk initialization during guest mode for better performance
• Updated components to use the new auth system

Guest Mode Infrastructure

• Added guest user support to Prisma schema with migrations
• Implemented guest session management with secure cookie handling
• Created guest banner component for clear user feedback
• Modified notebook routes to support guest user access

UI/UX Improvements

• Updated user navigation with guest-specific UI elements
• Added clear visual indicators for guest mode
• Maintained consistent UX across both auth modes

Technical Notes

• Guest sessions expire after 1 week
• Guest data is preserved in the database but isolated from authenticated users
• Clerk is only initialized for non-guest users
• Migration includes new fields: sessionId and isGuest for User model