fix: Add missing initial_index to startGame action type

frontend/src/store/gameStore.ts

@@ -47,6 +47,7 @@ export interface GameState {
     klines: KLine[];
     total_candles: number;
     initial_price: number;
+    initial_index: number;
   }) => void;
   nextCandle: () => void;
   buy: (volume: number) => boolean;