refactor(pricing): implement hybrid fee model (€0.50 + 1.5%) deducted from promoter payout

- Remove 1€ fixed fee from orders and Stripe invoices
- Add platform_fee_cents, promoter_payout_cents methods to Order model
- Update views to show clean ticket totals without added fees
- Update tests for new fee calculation logic
- Update pricing docs with implemented model

test/models/order_test.rb

@@ -469,7 +469,7 @@ class OrderTest < ActiveSupport::TestCase
     assert_equal "active", ticket2.status
   end
 
-  test "calculate_total! should sum ticket prices plus 1€ service fee" do
+  test "calculate_total! should sum ticket prices only (platform fee deducted from promoter payout)" do
     order = Order.create!(
       user: @user, event: @event, total_amount_cents: 0,
       status: "draft", payment_attempts: 0
@@ -506,7 +506,80 @@ class OrderTest < ActiveSupport::TestCase
     order.calculate_total!
     order.reload
 
-    assert_equal 3100, order.total_amount_cents # 2 tickets * 1500 cents + 100 cents (1€ fee)
+    assert_equal 3000, order.total_amount_cents # 2 tickets * 1500 cents (no service fee added to customer)
+  end
+
+  test "platform_fee_cents should calculate €0.50 + 1.5% per ticket" do
+    order = Order.create!(
+      user: @user, event: @event, total_amount_cents: 0,
+      status: "draft", payment_attempts: 0
+    )
+
+    ticket_type1 = TicketType.create!(
+      name: "Cheap Ticket",
+      description: "Cheap ticket type",
+      price_cents: 1000, # €10
+      quantity: 10,
+      sale_start_at: Time.current,
+      sale_end_at: Time.current + 1.day,
+      requires_id: false,
+      event: @event
+    )
+
+    ticket_type2 = TicketType.create!(
+      name: "Expensive Ticket",
+      description: "Expensive ticket type",
+      price_cents: 5000, # €50
+      quantity: 10,
+      sale_start_at: Time.current,
+      sale_end_at: Time.current + 1.day,
+      requires_id: false,
+      event: @event
+    )
+
+    ticket1 = Ticket.create!(order: order, ticket_type: ticket_type1, status: "draft", first_name: "John", last_name: "Doe")
+    ticket2 = Ticket.create!(order: order, ticket_type: ticket_type2, status: "draft", first_name: "Jane", last_name: "Doe")
+
+    expected_fee = (50 + (1000 * 0.015).to_i) + (50 + (5000 * 0.015).to_i) # 50+15 + 50+75 = 190
+    assert_equal 190, order.platform_fee_cents
+  end
+
+  test "promoter_payout_cents should be total minus platform fee" do
+    order = Order.create!(
+      user: @user, event: @event, total_amount_cents: 3000,
+      status: "paid", payment_attempts: 0
+    )
+
+    ticket_type = TicketType.create!(
+      name: "Test Ticket",
+      description: "Test ticket",
+      price_cents: 1500,
+      quantity: 10,
+      sale_start_at: Time.current,
+      sale_end_at: Time.current + 1.day,
+      requires_id: false,
+      event: @event
+    )
+
+    Ticket.create!(order: order, ticket_type: ticket_type, status: "active", first_name: "John", last_name: "Doe")
+    Ticket.create!(order: order, ticket_type: ticket_type, status: "active", first_name: "Jane", last_name: "Doe")
+
+    order.calculate_total! # Should still be 3000
+    expected_payout = 3000 - (50 + (1500 * 0.015).to_i) * 2 # 3000 - (50+22.5≈22)*2 = 3000 - 144 = 2856
+    assert_equal 2856, order.promoter_payout_cents
+  end
+
+  test "platform_fee_euros should convert cents to euros" do
+    order = Order.new(total_amount_cents: 0)
+    # Assuming one €10 ticket: 50 + 150 = 200 cents = €2.00
+    def order.platform_fee_cents; 200; end
+    assert_equal 2.0, order.platform_fee_euros
+  end
+
+  test "promoter_payout_euros should convert cents to euros" do
+    order = Order.new(total_amount_cents: 10000)
+    def order.platform_fee_cents; 500; end
+    assert_equal 95.0, order.promoter_payout_euros
   end
 
   # === Stripe Integration Tests (Mock) ===