Remove company information section from onboarding

Completely remove the enterprise/company information functionality from
the onboarding flow to simplify the user experience:

- Remove company information toggle section and form fields from view
- Delete unused Stimulus toggle controller (toggle_section_controller.js)
- Update onboarding controller to only process first/last name parameters
- Remove company_name from permitted parameters and validation logic
- Update tests to remove company name assertions and test cases
- Simplify onboarding to only collect essential personal information

The onboarding now focuses solely on collecting required first and last
names, providing a cleaner and faster user experience.

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

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

app/controllers/onboarding_controller.rb

@@ -22,7 +22,7 @@ class OnboardingController < ApplicationController
   private
 
   def onboarding_params
-    params.require(:user).permit(:first_name, :last_name, :company_name)
+    params.require(:user).permit(:first_name, :last_name)
   end
 
   def onboarding_params_valid?