fix: fe limit spawn rate

frontend/src/js/fight_scene.ts

@@ -315,7 +315,7 @@ function spawn(scene: any) {
   scene.time.now;
   const delay =
     (8 * 1000 * (60 * 1000 - scene.time.now)) / 60 / 1000 + 2 * 1000;
-  setTimeout(() => spawn(scene), delay);
+  setTimeout(() => spawn(scene), Math.max(delay, 2000));
 }
 
 function dispatchEnemy(scene: any) {