fix stockfish path

app.py

@@ -168,7 +168,7 @@ def get_top_moves(fen: str, top_n: int = 5) -> dict:
     import chess.engine
 
     board = chess.Board(fen)
-    with chess.engine.SimpleEngine.popen_uci("stockfish") as engine:
+    with chess.engine.SimpleEngine.popen_uci("/usr/games/stockfish") as engine:
         info = engine.analyse(board, chess.engine.Limit(time=2.0), multipv=top_n)
         top_moves = [
             {