feat(payouts): implement promoter earnings viewing, request flow, and admin Stripe processing with webhooks

Add model methods for accurate net calculations (€0.50 + 1.5% fees), eligibility, refund handling
Update promoter/payouts controller for index (pending events), create (eligibility checks)
Integrate admin processing via Stripe::Transfer, webhook for status sync
Enhance views: index pending cards, events/show preview/form
Add comprehensive tests (models, controllers, service, integration); run migrations

app/models/ticket.rb

@@ -22,6 +22,8 @@ class Ticket < ApplicationRecord
   before_validation :set_price_from_ticket_type, on: :create
   before_validation :generate_qr_code, on: :create
 
+  after_update :recalculate_earning_if_refunded, if: :saved_change_to_status?
+
   # Generate PDF ticket
   def to_pdf
     TicketPdfGenerator.new(self).generate
@@ -73,4 +75,12 @@ class Ticket < ApplicationRecord
   def draft?
     status == "draft"
   end
+
+  private
+
+  def recalculate_earning_if_refunded
+    if status == "refunded"
+      order.earning&.recalculate!
+    end
+  end
 end