feat: implement weekly MLOps retraining loop and specialized multi-model router

feat: add user strategy performance tracker table, lockInStrategy GraphQL mutation, and auto-labeler updates

feat: add MLOps prediction logs table, background labeling task, and model metrics endpoint

feat: add secure 6-digit OTP email verification flow

feat: implement subscription packages, message limit quotas, and 3-day discount timer

feat: implement real-time price alerts via email with 2-minute reminder loops

feat: implement AI Analyst strategy history and persistence

feat: define database models for User, Payments, Watchlist, Alert, and StockHistory

chore: initial project structure with uv config and gitignore