chore: revert memoization patterns and redundant default values

- Disable Style/MemoizeInstanceVariable and Style/RedundantAssignment rules
- Revert all instance_variable_defined? patterns back to ||= memoization
- Restore || 0 and || 1 default values that were removed by RuboCop
- Restore ternary operator formatting
- Reduce PR from 35 to 18 files by removing cosmetic style changes

app/controllers/api/v1/widget/base_controller.rb

@@ -25,11 +25,7 @@ class Api::V1::Widget::BaseController < ApplicationController
   end
 
   def inbox
-    if instance_variable_defined?(:@inbox)
-      @inbox
-    else
-      @inbox = ::Inbox.find_by(id: auth_token_params[:inbox_id])
-    end
+    @inbox ||= ::Inbox.find_by(id: auth_token_params[:inbox_id])
   end
 
   def conversation_params