fix: resolution of critical blockers (P0/P1/P2 fixes) - async Redis, atomic credit updates, schema compatibility, task event loop safety, rate limits, timezone datetimes

fix: all 9 production audit issues - DEBUG default, delete_account commit, guest session security, GitHub OAuth redirect, unlimited credits sentinel

Fix auto-login, SSE streams, LLM timeouts, and frontend cancellation

Initialize Archvise API backend for Hugging Face Spaces