Add appearance setting for 2 column layout (#1285)

app/models/user.rb

@@ -320,6 +320,10 @@ class User < ApplicationRecord
     preferences&.dig("show_split_grouped") != false
   end
 
+  def dashboard_two_column?
+    preferences&.dig("dashboard_two_column") != false
+  end
+
   def update_transactions_preferences(prefs)
     transaction do
       lock!