feat(武器): 为弓武器添加生命汲取和升华选项

添加生命汲取效果，使箭矢命中时回复生命值
实现弓武器的升华系统，包含5种不同品质的强化选项
调整攻击逻辑以支持升华效果和生命值相关的伤害加成

scripts/Contents/Bullets/Bow.gd

@@ -4,20 +4,22 @@ class_name Bow
 var count: int = 0
 var atk: float = 0
 var waitTime: float = 2000
+var lifesteal: float = 0.2
 
 func spawn():
 	var startAngle = rotation - deg_to_rad(count * 10.0 / 2)
 	for c in count:
-		for i in BulletBase.generate(
+		for bullet in BulletBase.generate(
 			ComponentManager.getBullet("Arrow"),
 			launcher,
 			position,
 			startAngle
 		):
-			var bullet: Arrow = i
-			bullet.atk = atk
-			bullet.waitTime = waitTime
-			bullet.offsetRotation = deg_to_rad(c * 10.0)
+			if bullet is Arrow:
+				bullet.atk = atk
+				bullet.waitTime = waitTime
+				bullet.offsetRotation = deg_to_rad(c * 10.0)
+				bullet.lifesteal = lifesteal
 	await TickTool.millseconds(waitTime)
 	tryDestroy()
 func ai():