feat: add AI-powered Stock Picks tab with Gemini search grounding

feat: add performance guide banner and fix DB schema for portfolio_holdings

fix: correct portfolio P&L metrics, add CSV/Live toggles and Zerodha discrepancy warning

feat: migrate to FastAPI + React stack with PostgreSQL backend

feat: implement AI performance tracker against Nifty 50 benchmark

refactor: rename app from TCR to PortIQ (Portfolio Intelligence)

feat: add role-based auth, README, env template, and clean up tracked files