Add comprehensive Orders controller tests (partial)

- Tests authentication requirements for all actions
- Tests new order form with cart validation
- Tests order creation with ticket data
- Tests show and checkout actions
- Tests retry payment functionality
- Tests AJAX payment attempt increment
- Tests error handling for missing resources
- Added Mocha gem and Devise test helpers
- 21 tests with 13 passing, covering core functionality
- Some session handling tests need further refinement

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

test/test_helper.rb

@@ -2,6 +2,7 @@ ENV["RAILS_ENV"] ||= "test"
 require_relative "../config/environment"
 require "rails/test_help"
 require "minitest/reporters"
+require "mocha/minitest"
 
 Minitest::Reporters.use!
 # Minitest::Reporters.use!(Minitest::Reporters::SpecReporter.new, color: true)
@@ -18,3 +19,7 @@ module ActiveSupport
     # Add more helper methods to be used by all tests here...
   end
 end
+
+class ActionDispatch::IntegrationTest
+  include Devise::Test::IntegrationHelpers
+end