feat(音效): 添加物品收集音效并改进数值显示

为物品收集添加音效播放功能
在EntityBase.gd中调用playSound("collect")
添加Collect.wav音效文件及导入配置

改进数值显示格式：
- 在MathTool.gd中添加signBeforeStr方法
- 修改FieldShow.gd使用新方法显示带符号的数值
- 调整FieldShow.tscn的UI布局

同时修复MakeFeed.gd中feed显示问题

scripts/Contents/Panels/MakeFeed.gd

@@ -60,5 +60,6 @@ func regenerateCards():
 	feeds.shuffle()
 	for i in range(UIState.player.fields[FieldStore.Entity.FEED_COUNT_SHOW]):
 		var feed = feeds[i] as Feed
+		feed.show()
 		avaliableFeeds.remove_child(feed)
 		feedCards.add_child(feed)

scripts/Statemachine/EntityBase.gd

@@ -71,6 +71,7 @@ func _ready():
 			func(body):
 				if body is ItemDropped:
 					inventory[body.item] += body.stackCount
+					playSound("collect")
 					body.queue_free()
 		)
 		energyChanged.connect(

scripts/Statemachine/FieldShow.gd

@@ -13,9 +13,9 @@ func _ready():
 	var formattedValue: String
 	var dataType = FieldStore.entityMapType[field]
 	if dataType == FieldStore.DataType.VALUE:
-		formattedValue = str(value)
+		formattedValue = MathTool.signBeforeStr(value)
 	elif dataType == FieldStore.DataType.ANGLE:
-		formattedValue = str(value) + "°"
+		formattedValue = MathTool.signBeforeStr(value) + "°"
 	elif dataType == FieldStore.DataType.PERCENT:
-		formattedValue = "%.1f" % (value * 100) + "%"
+		formattedValue = MathTool.signBeforeStr(float("%.1f" % (value * 100))) + "%"
 	valueLabel.text = formattedValue

scripts/Tools/MathTool.gd

@@ -8,4 +8,6 @@ static func randv2_range(offset: float):
 		randf_range(-offset, offset)
 	)
 static func randc_from(array: Array):
-	return array[randi() % array.size()]
+	return array[randi() % array.size()]
+static func signBeforeStr(value: float):
+	return ("+" if value > 0 else "-" if value < 0 else "") + str(abs(value))