feat: add portfolio summary to simulation page

Shows real-time portfolio metrics:
- Cash Balance
- Position (quantity and value)
- Entry Price / Current Price
- Unrealized P&L
- Total Value
- P&L (absolute and percentage)

Updates as simulation runs and trades are executed.

src/backend/app/api/simulate.py

@@ -60,6 +60,9 @@ def run_simulation_sync(
                         for k in engine.klines
                     ]
                     simulation.trade_log = engine.trade_log
+                    # Save portfolio data
+                    if hasattr(engine, 'current_balance') and engine.current_balance is not None:
+                        simulation.signals = [serialize_signal(s) for s in engine.signals]
                     db.commit()
             finally:
                 db.close()

src/backend/app/services/simulate/engine.py

@@ -169,6 +169,14 @@ class SimulateEngine:
         self.results["total_candles"] = self.total_candles
         self.results["klines"] = self.klines  # Include klines for chart display
         self.results["trade_log"] = self.trade_log  # Include trade log for dashboard
+        self.results["portfolio"] = {
+            "initial_balance": self.config.get("initial_balance", 10000),
+            "current_balance": self.current_balance,
+            "position": self.position,
+            "position_token": self.position_token,
+            "entry_price": self.entry_price,
+            "current_price": self.last_close,
+        }
         self.results["started_at"] = self.started_at
         self.results["ended_at"] = datetime.utcnow()