fix: use existsSync instead of require(fs) in ESM module

server/src/controllers/stockfish.controller.ts

@@ -1,4 +1,5 @@
 import { spawn, ChildProcess } from "child_process";
+import { existsSync } from "fs";
 
 export interface StockfishLevel {
     level: number;
@@ -32,8 +33,7 @@ export class StockfishEngine {
         try {
             // Debian installs stockfish to /usr/games/stockfish
             const sfBin = ["/usr/games/stockfish", "/usr/bin/stockfish", "stockfish"]
-                .find(p => { try { require("fs").accessSync(p); return true; } catch { return false; } })
-                ?? "stockfish";
+                .find(p => existsSync(p)) ?? "stockfish";
 
             this.process = spawn(sfBin, [], {
                 stdio: ["pipe", "pipe", "pipe"],