C1: Fix BacktestDataLoader constructor args (was passing wrong kwargs)
C2: Fix BacktestResult attribute names (max_drawdown_pct, avg_hold_duration)
C3: Remove insecure JWT secret default (now required via env var)
C4: Fix .env.example to use TRADING_ prefix for all config vars
C5: Add missing fields to portfolio endpoint (daily_pnl_pct, total_pnl, trading_active)
C6: Add missing /portfolio/metrics endpoint
C7: Add 'value' field to equity curve response for frontend compatibility
C8: Add 6M/ALL periods and case-insensitive period enum parsing
Also: make app creation lazy to avoid config validation at import time
