feat: add Portfolio Value, Option Value, and Contracts columns to daily results

- Add option_contracts field to BacktestDailyPoint (number of contracts held)
- Update engine to calculate total option contracts from positions
- Update job serialization to include underlying_value, option_market_value, net_portfolio_value, option_contracts
- Update both render_result and render_job_result tables to show:
  - Low, High, Close (from previous commit)
  - Portfolio value (net_portfolio_value)
  - Option value (option_market_value)
  - Contracts (option_contracts)
  - LTV hedged
  - Margin call status

app/models/backtest.py

@@ -97,10 +97,12 @@ class BacktestDailyPoint:
     ltv_hedged: float
     margin_call_unhedged: bool
     margin_call_hedged: bool
+    active_position_ids: tuple[str, ...] = field(default_factory=tuple)
     # Optional OHLC fields for worst-case margin call evaluation
     spot_low: float | None = None  # Day's low for margin call evaluation
     spot_high: float | None = None  # Day's high
-    active_position_ids: tuple[str, ...] = field(default_factory=tuple)
+    # Option position info
+    option_contracts: float = 0.0  # Number of option contracts held
 
 
 @dataclass(frozen=True)
@@ -154,3 +156,22 @@ class EventComparisonReport:
     scenario: BacktestScenario
     rankings: tuple[EventComparisonRanking, ...]
     run_result: BacktestRunResult
+
+
+@dataclass(frozen=True)
+class BacktestPortfolioPreset:
+    """User-facing preset for quick scenario configuration."""
+
+    preset_id: str
+    name: str
+    description: str
+    underlying_symbol: str
+    start_date: date
+    end_date: date
+    entry_spot: float | None = None  # If None, derive from historical data
+    underlying_units: float = 1000.0
+    loan_amount: float = 50000.0
+    margin_call_ltv: float = 0.80
+    template_slug: str = "protective-put-atm-12m"
+    # Event-specific overrides
+    scenario_overrides: dict[str, object] | None = None