fix: respect candle_delay from config, default to fast tests

- Tests now run with candle_delay=0 for fast execution
- Simulation defaults to candle_delay based on interval (e.g., 30s for 1m)
- Progress saved to DB every 5 seconds during simulation
- User can now see real-time updates while simulation runs

Tests: 14 passing in 0.15s

src/frontend/src/lib/api/types.ts

@@ -118,6 +118,9 @@ export interface Simulation {
 	signals: Signal[] | null;
 	klines?: { time: number; close: number }[];
 	trade_log?: TradeLogEntry[];
+	current_candle_index?: number;
+	total_candles?: number;
+	candles_processed?: number;
 }
 
 export interface SimulationConfig {