Add promotion details and modal to orders and promotions

Introduces promotion-related fields to the Order interface and displays promotion discounts in both the order details and order table. Adds a PromotionDetailsModal component for viewing detailed promotion analytics and eligibility, and integrates it into the PromotionsList with a new 'view details' action.

app/dashboard/orders/[id]/page.tsx

@@ -69,6 +69,11 @@ interface Order {
   lastBalanceReceived?: number;
   cryptoTotal?: number;
   paymentAddress?: string;
+  // Promotion fields
+  promotion?: string;
+  promotionCode?: string;
+  discountAmount?: number;
+  subtotalBeforeDiscount?: number;
 }
 
 interface OrderInList extends Order {
@@ -697,6 +702,17 @@ export default function OrderDetailsPage() {
                       <TableCell className="text-right font-medium">Shipping ({order?.shippingMethod.type})</TableCell>
                       <TableCell className="text-right">£{order?.shippingMethod.price.toFixed(2)}</TableCell>
                     </TableRow>
+                    {order?.promotionCode && order?.discountAmount && order?.discountAmount > 0 && (
+                      <TableRow>
+                        <TableCell colSpan={2} />
+                        <TableCell className="text-right font-medium text-green-600">
+                          Promotion ({order.promotionCode})
+                        </TableCell>
+                        <TableCell className="text-right text-green-600">
+                          -£{order.discountAmount.toFixed(2)}
+                        </TableCell>
+                      </TableRow>
+                    )}
                     <TableRow>
                       <TableCell colSpan={2} />
                       <TableCell className="text-right font-bold">Total</TableCell>