Trades: an open position shows no close price or P&L

Vest's position history gives an open position a placeholder close price
and a $0 P&L (290.25 on an NDX short at 29,538.96). Only a closed
position keeps them now — in the parser, in the stored row (a placeholder
already stored is cleared on the next read) and in the API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/api/trades/route.ts

@@ -41,8 +41,8 @@ export async function GET(req: Request) {
             side: t.side,
             quantity: t.quantity,
             openPrice: t.openPrice,
-            closePrice: t.closePrice,
-            pnl: t.pnl,
+            closePrice: open ? null : t.closePrice,
+            pnl: open ? null : t.pnl,
             fee: t.fee,
             funding: t.funding,
             net,