fix: improve tag formatting functionality

- Update `format_as_tag` method to replace hyphens with
  underscores in addition to spaces.
- Ensure the method handles blank inputs properly.

This change improves the consistency of tag formatting by
ensuring that both spaces and hyphens are converted into
underscores, enhancing the usability and reliability of
this helper method.

app/helpers/tag_helper.rb

@@ -2,9 +2,8 @@ module TagHelper
   def format_as_tag(text)
     return nil if text.blank?
 
-    # 空格改为下划线
-    text.strip.gsub(/\s+/, "_")
-    text.strip.gsub("-", "_")
+    # 空格改为下划线, 中划线改为下划线
+    text.strip.gsub(/\s+/, "_").gsub("-", "_")
 
     # 或者删除空格 (选项2)
     # text.strip.gsub(/\s+/, '')