fix(fade-kit): 修复 FadeKit 空引用和零时长异常

- 增加 Image 空引用保护
- 处理 duration 小于等于 0 的边界情况
- 动画开始前调用 DOKill 避免冲突
- 使用 DOFade 替代 DOBlendableColor，行为更明确

Assets/Scripts/Framework/OtherKit/FadeKit.cs

@@ -9,42 +9,74 @@ namespace AibisDream.Framework
     {
         public static IEnumerator FadeInAsync(this Image image, float duration, bool useUnscaledTime = false)
         {
-            image.gameObject.SetActive(true);
-            var tweener = image.DOBlendableColor(Color.white, duration);
-            if (useUnscaledTime)
+            var tweener = StartFade(image, 1f, duration, useUnscaledTime);
+            if (tweener != null)
             {
-                tweener.SetUpdate(true);
+                yield return tweener.WaitForCompletion();
             }
-
-            yield return tweener.WaitForCompletion();
         }
 
         public static void FadeIn(this Image image, float duration)
         {
-            image.gameObject.SetActive(true);
-            var tweener = image.DOBlendableColor(Color.white, duration);
+            StartFade(image, 1f, duration, false);
         }
 
         public static IEnumerator FadeOutAsync(this Image image, float duration, bool useUnscaledTime = false)
         {
-            image.gameObject.SetActive(true);
-            var tweener = image.DOBlendableColor(Color.clear, duration);
-            if (useUnscaledTime)
+            var completed = false;
+            var tweener = StartFade(image, 0f, duration, useUnscaledTime);
+            if (tweener == null)
             {
-                tweener.SetUpdate(true);
+                image?.gameObject.SetActive(false);
+                yield break;
             }
 
+            tweener.OnComplete(() => completed = true);
             yield return tweener.WaitForCompletion();
-            image.gameObject.SetActive(false);
+            if (completed && image != null)
+            {
+                image.gameObject.SetActive(false);
+            }
         }
 
         public static void FadeOut(this Image image, float duration)
         {
-            image.gameObject.SetActive(true);
-            image.DOBlendableColor(Color.clear, duration).onComplete += () =>
+            var tweener = StartFade(image, 0f, duration, false);
+            if (tweener == null)
             {
-                image.gameObject.SetActive(false);
-            };
+                image?.gameObject.SetActive(false);
+                return;
+            }
+
+            tweener.OnComplete(() =>
+            {
+                if (image != null)
+                {
+                    image.gameObject.SetActive(false);
+                }
+            });
+        }
+
+        private static Tweener StartFade(Image image, float targetAlpha, float duration, bool useUnscaledTime)
+        {
+            if (image == null)
+            {
+                return null;
+            }
+
+            image.DOKill(false);
+            image.gameObject.SetActive(true);
+
+            duration = Mathf.Max(0f, duration);
+            if (duration <= 0f)
+            {
+                var color = image.color;
+                color.a = targetAlpha;
+                image.color = color;
+                return null;
+            }
+
+            return image.DOFade(targetAlpha, duration).SetUpdate(useUnscaledTime);
         }
     }
-}
+}