fix: Only increment payment attempts when user actually attempts payment

- Remove payment attempt increment from checkout page load
- Add new increment_payment_attempt action triggered only on pay button click
- Update checkout JavaScript to make AJAX call before Stripe redirect
- Add proper error handling and button state management
- Prevent inflated payment attempt counts from page refreshes

This ensures payment attempts accurately reflect actual payment tries rather than page visits.

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

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

config/routes.rb

@@ -43,6 +43,7 @@ Rails.application.routes.draw do
     member do
       get :checkout
       post :retry_payment
+      post :increment_payment_attempt
     end
   end