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/integration/payout_flow_test.rb

@@ -0,0 +1,58 @@
+require "test_helper"
+
+class PayoutFlowTest < ActionDispatch::IntegrationTest
+  setup do
+    @promoter = User.create!(email: "promoter@example.com", password: "password123", password_confirmation: "password123", is_professionnal: true)
+    @buyer = User.create!(email: "buyer@example.com", password: "password123", password_confirmation: "password123")
+    sign_in @promoter
+  end
+
+  test "full payout flow with refund" do
+    # Create event and ticket type
+    event = Event.create!(name: "Test Event", slug: "test-event", description: "This is a test event description that meets the minimum length requirement of 10 characters.", venue_name: "Venue", venue_address: "Address", latitude: 48.0, longitude: 2.0, start_time: 1.day.ago, end_time: 1.hour.ago, user: @promoter, state: :published)
+    ticket_type = TicketType.create!(event: event, name: "Standard", price_cents: 1000, quantity: 10, sale_start_at: 2.days.ago, sale_end_at: Time.current)
+
+    # Buyer purchases ticket (mock Stripe)
+    sign_in @buyer
+    Stripe::Checkout::Session.expects(:create).returns(stub(id: "cs_test"))
+
+    post event_checkout_path(event), params: { cart: { ticket_types: { ticket_type.id => 1 } } }
+    session_id = assigns(:session_id)
+    # Assume payment success creates order and tickets
+    order = Order.last
+    ticket = Ticket.last
+    assert_equal "paid", order.status
+    assert_equal "active", ticket.status
+
+    # Earnings created
+    earning = Earning.last
+    assert_not_nil earning
+    assert_equal 900, earning.amount_cents
+
+    # Refund one ticket
+    sign_in @promoter
+    ticket.update!(status: "refunded")
+    earning.reload
+    assert_equal 0, earning.amount_cents  # Recalculated
+
+    # Request payout
+    assert event.can_request_payout?(@promoter)
+    post promoter_payouts_path, params: { event_id: event.id }
+    payout = Payout.last
+    assert_equal :pending, payout.status
+
+    # Admin process
+    admin = User.create!(email: "admin@example.com", password: "password123", password_confirmation: "password123")
+    admin.add_role :admin
+    sign_in admin
+    Stripe::Transfer.expects(:create).returns(stub(id: "tr_success"))
+    patch admin_payout_path(payout)
+    payout.reload
+    assert_equal :completed, payout.status
+
+    # Webhook succeeds
+    post stripe_webhooks_path, params: { type: "payout.succeeded", data: { object: { id: "po_123" } } }, headers: { "Stripe-Signature" => "valid_sig" }
+    payout.reload
+    assert_equal :completed, payout.status  # Confirmed
+  end
+end