refactor: migrate refresh token storage from PostgreSQL table to Redis and remove associated DB schema.

perf: offload Supabase audit writes to background tasks for optimized refresh response times

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

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

refactor: remove HF token dependency, switch to text/plain token exchange

logging: add diagnostic logs for refresh token failures

refactor: adjust cookie samesite and secure attributes based on environment for authentication routes

refactor: expand JWT algorithm support

refactor: implement stateless Supabase JWT validation to resolve 403 race conditions

feat: implement stateless JWT-based authentication with refresh tokens stored in HTTPOnly Cookies

feat: optimize auth concurrency and enable full account deletion

feat: implement in-memory email rate limiting and adjust RAG search parameters

feat: implement password update functionality and add signup, forgot-password, and update-password pages

feat: move auth constants to dedicated module and add unit tests for avatar upload functionality

feat: implement profile avatar upload functionality to Supabase storage

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

feat: improve profile synchronization to prevent usage counter resets

feat: implement profile caching and optimize database client initialization.

refactor: remove unnecessary sign up page

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

fix: use Supabase Auth for real access tokens on login/signup

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