feat(掉落系统): 根据敌人等级调整boss掉落物品数量

将boss掉落的晶体数量上限从固定20改为15+等级，钻石数量上限从固定3改为等于等级

scripts/Statemachine/EntityBase.gd

@@ -416,7 +416,7 @@ func tryDie(by: BulletBase = null):
 			fields[FieldStore.Entity.MAX_HEALTH] * randf_range(1 - GameRule.beachballOffset, 1 + GameRule.beachballOffset),
 			position + MathTool.sampleInCircle(GameRule.itemDroppedSpawnOffset)
 		)
-		for i in randi_range(0, 20 if isBoss else 5):
+		for i in randi_range(0, (15 + level) if isBoss else 5):
 			ItemDropped.generate(
 				ItemStore.ItemType.CRYSTAL,
 				5 if isBoss else 1,
@@ -425,7 +425,7 @@ func tryDie(by: BulletBase = null):
 		if isBoss:
 			ItemDropped.generate(
 				ItemStore.ItemType.DIAMOND,
-				randi_range(1, 3),
+				randi_range(1, level),
 				position + MathTool.sampleInCircle(GameRule.itemDroppedSpawnOffset)
 			)
 	if isBoss: