fix(service): 更新字符缓存策略为删除而非刷新

原“刷新缓存”逻辑改为“删除缓存”，保证下次读取必从数据库加载最新数据，避免脏读

keyboard-server/src/main/java/com/yolo/keyboard/service/character/KeyboardCharacterServiceImpl.java

@@ -56,8 +56,8 @@ public class KeyboardCharacterServiceImpl implements KeyboardCharacterService {
         KeyboardCharacterDO updateObj = BeanUtils.toBean(updateReqVO, KeyboardCharacterDO.class);
         characterMapper.updateById(updateObj);
 
-        // 同步刷新 Redis 缓存，避免读取到旧数据
-        refreshCharacterCache(updateReqVO.getId());
+        // 删除 Redis 缓存，下次读取时再从数据库加载最新数据
+        deleteCharacterCache(updateReqVO.getId());
     }
 
     @Override