feat(武器系统): 添加核弹武器及相关资源

实现核弹武器功能，包括：
- 添加核弹控制器武器脚本和场景
- 实现核弹子弹逻辑和爆炸效果
- 添加相关图片、音效资源
- 更新角色武器库包含核弹
- 调整武器名称颜色配置

scripts/Contents/Bullets/NuclearBomb.gd

@@ -0,0 +1,23 @@
+extends BulletBase
+class_name NuclearBomb
+
+@onready var label: Label = $"%label"
+@onready var anchor: Node2D = $"%anchor"
+
+var countdown = 10000
+var radius = 500
+
+func spawn():
+	hitbox.disabled = true
+	hitbox.shape.radius = radius
+	anchor.global_rotation = 0
+func ai():
+	speed *= 0.99
+	PresetBulletAI.forward(self, rotation)
+	label.text = "NUCLEAR WARNING %.1f" % ((countdown - timeLived()) / 1000)
+	if timeLived() > countdown:
+		tryDestroy()
+func destroy(_b):
+	EffectController.create(preload("res://components/Effects/NuclearExplosion.tscn"), global_position).shot()
+	hitbox.disabled = false
+	await TickTool.frame(5)