Backtest runner: added per-trade fee simulation (maker 2bps, taker 5bps).
Each trade now records pnl_gross, pnl_net, and fee. New --no-fees flag
excludes fees from PnL. Output includes pnl_gross/pnl_gross_pct and
fees_total alongside existing pnl (net). Regenerated all 12 backtests.
Server: added /api/backtest/{name}/csv endpoint — returns trades as CSV
with columns time,side,size,price,pnl_gross,pnl_net,fee.
Content-Disposition: attachment triggers browser download.
Dashboard: added "Inc. fees" checkbox toggle in backtest detail panel.
Unchecking shows gross PnL (before fees). "↓ CSV" button downloads
the trade history. Both hidden when detail is closed.