feat: 首页配置封面图上传预览，修复系列活动跳转，活动卡片样式优化

backend/competition/serializers.py

@@ -17,7 +17,8 @@ class HomePageConfigSerializer(serializers.ModelSerializer):
     class Meta:
         model = HomePageConfig
         fields = ['id', 'banner_image', 'banner_image_url', 'display_banner',
-                  'main_title', 'organizer', 'undertaker']
+                  'main_title', 'organizer', 'undertaker', 'is_active']
+
     def get_display_banner(self, obj):
         return _media_url(obj.banner_image) or obj.banner_image_url