fix: add missing total_earnings_cents method and payout method to Event model

- Add alias total_earnings_cents for total_gross_cents for template compatibility
- Add payout method to get the latest payout for an event
- Fixes NoMethodError in promoter events earnings preview template

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

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

app/models/event.rb

@@ -76,6 +76,9 @@ class Event < ApplicationRecord
     tickets.active.sum(:price_cents)
   end
 
+  # Alias for template compatibility
+  alias_method :total_earnings_cents, :total_gross_cents
+
   def total_fees_cents
     earnings.pending.sum(:fee_cents)
   end
@@ -88,6 +91,11 @@ class Event < ApplicationRecord
     event_ended? && (net_earnings_cents > 0) && user.is_professionnal? && payouts.pending.empty?
   end
 
+  # Get the latest payout for this event
+  def payout
+    payouts.order(created_at: :desc).first
+  end
+
   # Check if coordinates were successfully geocoded or are fallback coordinates
   def geocoding_successful?
     coordinates_look_valid?