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>

Gemfile

@@ -73,6 +73,8 @@ group :test do
   gem "selenium-webdriver"
   # For controller testing helpers
   gem "rails-controller-testing"
+  # For mocking and stubbing
+  gem "mocha"
 end
 
 gem "devise", "~> 4.9"