sources: fix dummy names being suggested as other names.

Fix placeholder names like weibo_1234, bilibili_1234, nijie1234, and nicoseiga1234 being suggested
as Other Names when creating new artist entries. These are meant to be placeholders for the tag
name, not used as other names.

app/logical/source/extractor/tinami.rb

@@ -56,7 +56,11 @@ module Source
       end
 
       def tag_name
-        nil
+        "tinami_#{user_id}" if user_id.present?
+      end
+
+      def other_names
+        [artist_name].compact
       end
 
       def artist_name