Add fee-toggle for backtests, CSV trade download, fee simulation in runner

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.

dashboard/server.py

@@ -195,6 +195,29 @@ async def get_backtest(name: str):
     return JSONResponse({"error": "not found"}, status_code=404)
 
 
+@app.get("/api/backtest/{name}/csv")
+async def get_backtest_csv(name: str):
+    """Download backtest trades as CSV."""
+    from fastapi.responses import Response
+    fpath = os.path.join(BACKTEST_DIR, f"{name}.json")
+    if not os.path.exists(fpath):
+        return JSONResponse({"error": "not found"}, status_code=404)
+    with open(fpath) as f:
+        data = json.load(f)
+    trades = data.get("trades", [])
+    # Build CSV with headers
+    header = "time,side,size,price,pnl_gross,pnl_net,fee\n"
+    rows = []
+    for t in trades:
+        rows.append(f"{t.get('time','')},{t.get('side','')},{t.get('size','')},{t.get('price','')},{t.get('pnl_gross',t.get('pnl',''))},{t.get('pnl_net',t.get('pnl',''))},{t.get('fee','0')}")
+    csv_content = header + "\n".join(rows)
+    return Response(
+        content=csv_content,
+        media_type="text/csv",
+        headers={"Content-Disposition": f"attachment; filename={name}_trades.csv"}
+    )
+
+
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