refactor: replace daily usage increment with atomic reservation

refactor: replace standard logging with a centralized loguru configuration and interception handler

feat: implement Redis-first refresh token storage with Supabase fallback

feat: implement LLM fallback for quiz generation and enhance OAuth error handling

refactor: decouple usage increment from rate limit checks, add session refresh error handling.

feat: increase quiz generation capacity with dedicated high-token LLM.

refactor: changing to gemini model, modularize constants and schemas and update user daily generation limit

fix: improve security, session handling, and UI responsiveness for topic management and document rendering

feat: implement profile caching and optimize database client initialization.

feat: disable renaming for topics and transition to per-user title uniqueness constraints

refactor: implement async execution for blocking database operations and add title collision auto-increment for new materials

fix: improve PDF print layout and normalize 'topic' source type handling

feat: implement persistent user theme preferences across client and backend with profile synchronization

refactor: replace legacy login page with integrated Google OAuth landing page and dashboard redirect logic

feat: implement daily request rate limiting with per-user usage tracking and admin bypass

feat: implement search functionality, add background task queue logic for title conflicts, and enhance auth state synchronization

refactor: improve markdown parsing, update summary export formatting, and refine UI loading states for material summaries

feat: Adding Parallel Processing and enhance main dashboard, summary and chat styles

feat: implement Supabase token authentication and migrate user management to profiles table

feat: implement authentication system, add quiz history support, and update API endpoints for material and tutor interactions

refactor: restructure project into modular src architecture and implement database store layer