feat: Implement comprehensive onboarding system for new users

Add complete user onboarding flow that redirects new users to complete their
profile before accessing the application:

- Add onboarding_completed boolean field to users with migration
- Create OnboardingController with form validation and completion logic
- Design professional onboarding UI with progressive disclosure for company info
- Implement Stimulus controller for toggling company information section
- Add application-wide redirect middleware for incomplete users
- Create comprehensive test suite for all onboarding functionality
- Update test fixtures and helpers to support onboarding in existing tests

The onboarding collects required first/last name and optional company information.
Users are redirected to onboarding after login until profile is completed.
Features smooth animations, full-width form button, and clean UX design.

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

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

test/controllers/orders_controller_test.rb

@@ -5,7 +5,10 @@ class OrdersControllerTest < ActionDispatch::IntegrationTest
     @user = User.create!(
       email: "test@example.com",
       password: "password123",
-      password_confirmation: "password123"
+      password_confirmation: "password123",
+      onboarding_completed: true,
+      first_name: "Test",
+      last_name: "User"
     )
 
     @event = Event.create!(