feat(help-center): enable drag-and-drop category reordering (#13706)

app/models/portal.rb

@@ -27,6 +27,8 @@
 class Portal < ApplicationRecord
   include Rails.application.routes.url_helpers
 
+  DEFAULT_COLOR = '#1f93ff'.freeze
+
   belongs_to :account
   has_many :categories, dependent: :destroy_async
   has_many :folders,  through: :categories
@@ -62,6 +64,10 @@ class Portal < ApplicationRecord
     config['default_locale'] || 'en'
   end
 
+  def color
+    self[:color].presence || DEFAULT_COLOR
+  end
+
   private
 
   def config_json_format