add paper trading: mark a setup as taken, track open P&L, sell

New paper_trades table (migration 007) + service/router. "Mark as taken" on each
setup card (shares prefilled from position sizing, entry from current price, both
editable) records a simulated trade. Overview gains an Open Trades table that
marks each position to the latest close — P&L in $, %, and R-multiples — with a
total unrealized P&L footer and a Sell button to close at the current price.
Closed trades are retained for future realized-P&L reporting.

Deploy: alembic upgrade (new paper_trades table).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/pages/DashboardPage.tsx

@@ -8,6 +8,7 @@ import { useMarketRegime } from '../hooks/useMarketRegime';
 import { regimeColor, regimeDot, regimeHeadline } from '../lib/regime';
 import { Callout } from '../components/ui/Callout';
 import { Section } from '../components/ui/Section';
+import { OpenTradesPanel } from '../components/dashboard/OpenTradesPanel';
 import { SkeletonCard, SkeletonTable } from '../components/ui/Skeleton';
 import { formatPrice } from '../lib/format';
 import { recommendationActionLabel } from '../lib/recommendation';
@@ -150,6 +151,9 @@ export default function DashboardPage() {
         </div>
       )}
 
+      {/* Open paper trades */}
+      <OpenTradesPanel />
+
       <div className="grid gap-8 xl:grid-cols-5">
         {/* Top setups */}
         <div className="xl:col-span-3">