feat(子弹效果): 为七魂子弹添加粒子效果并调整颜色逻辑

修改子弹脚本以支持粒子效果发射
调整颜色应用逻辑从heart节点转移到父节点
为SoulBall和SevenSoul场景添加粒子系统配置

scripts/Contents/Bullets/SevenSoul.gd

@@ -11,9 +11,11 @@ var colors = [
 var index = 0
 
 @onready var heart = $"%heart"
+@onready var effect: GPUParticles2D = $"%effect"
 
 func spawn():
-	heart.modulate = Color(colors[index % colors.size()])
+	modulate = Color(colors[index % colors.size()])
+	effect.emitting = true
 func ai():
 	rotation_degrees = 360.0 / colors.size() * index + timeLived() / 20000.0 * 360 - index / 6.0 * 360.0
 	heart.global_rotation_degrees = 0