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/lib/paperTrade.ts

@@ -0,0 +1,25 @@
+import type { PaperTrade } from './types';
+
+export interface TradePnl {
+  /** Reference price: live close for open trades, exit price for closed. */
+  ref: number;
+  perShare: number;
+  pnl: number;
+  pct: number;
+  /** Profit in R-multiples (relative to the per-share risk), null if no risk. */
+  r: number | null;
+}
+
+export function tradePnl(t: PaperTrade): TradePnl | null {
+  const ref = t.current_price;
+  if (ref == null || !t.entry_price) return null;
+  const perShare = t.direction === 'long' ? ref - t.entry_price : t.entry_price - ref;
+  const risk = Math.abs(t.entry_price - t.stop_loss);
+  return {
+    ref,
+    perShare,
+    pnl: perShare * t.shares,
+    pct: (perShare / t.entry_price) * 100,
+    r: risk > 0 ? perShare / risk : null,
+  };
+}

frontend/src/lib/types.ts

@@ -179,6 +179,21 @@ export interface SentimentProviderConfig {
   custom_base_url_providers: string[];
 }
 
+export interface PaperTrade {
+  id: number;
+  symbol: string;
+  direction: 'long' | 'short';
+  entry_price: number;
+  shares: number;
+  stop_loss: number;
+  target: number;
+  status: 'open' | 'closed';
+  opened_at: string;
+  close_price: number | null;
+  closed_at: string | null;
+  current_price: number | null;
+}
+
 export interface BacktestBucket {
   total: number;
   wins: number;