Add comprehensive unit test coverage for controllers, models, and services

- Translate French comments to English in controllers and tests
- Fix test failures: route helpers, validations, MySQL transaction issues
- Add Timecop for time-dependent tests and update database config for isolation

test/test_helper.rb

@@ -12,6 +12,7 @@ module ActiveSupport
   class TestCase
     # Run tests in parallel with specified workers
     parallelize(workers: :number_of_processors)
+    use_transactional_fixtures = true
 
     # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
     fixtures :all