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

test/models/earning_test.rb

@@ -83,4 +83,53 @@ class EarningTest < ActiveSupport::TestCase
     assert_not_includes Earning.paid, pending_earning
     assert_includes Earning.paid, paid_earning
   end
+  # Payout-related tests
+
+  test "creation from order" do
+    user = users(:one)
+    event = events(:concert_event)
+    order = orders(:paid_order)
+    order.update!(status: "paid", total_amount_cents: 10000)
+
+    # Assume Earning.create_from_order(order) or callback creates earning
+    Earning.create_from_order(order)
+
+    earning = Earning.where(order: order).first
+    assert_not_nil earning
+    assert_equal 9000, earning.amount_cents  # After fees: assume 10% fee or based on ticket
+    assert_equal 1000, earning.fee_cents
+    assert earning.pending?
+  end
+
+  test "recalculation on full refund" do
+    earning = earnings(:one)
+    earning.amount_cents = 1000
+    earning.fee_cents = 100
+    earning.save!
+
+    # Assume all tickets in order refunded
+    order = orders(:one)
+    order.tickets.each { |t| t.update!(status: "refunded") }
+
+    earning.recalculate_on_refund(order)
+
+    assert_equal 0, earning.amount_cents
+    assert earning.refunded?  # Assume status update
+  end
+
+  test "recalculation on partial refund" do
+    earning = earnings(:one)
+    earning.amount_cents = 2000
+    earning.fee_cents = 200
+    earning.save!
+
+    order = orders(:one)
+    # Refund one ticket of 1000
+    order.tickets.first.update!(status: "refunded")
+
+    earning.recalculate_on_refund(order)
+
+    assert_equal 1000, earning.amount_cents  # Half
+    assert_equal 100, earning.fee_cents  # Half
+  end
 end