Add formula-based product pricing (P/W/MG) for Parsian-style unit prices.

Port FormulaPriceService from colleague app so admins can compute a single unit price from reference mid, weight, and wage instead of offset coefficients.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Services/ZaarboxPriceService.php

@@ -739,6 +739,13 @@ class ZaarboxPriceService
             return 0;
         }
 
+        if (FormulaPriceService::isEnabled($product)) {
+            return FormulaPriceService::calculateForProduct($product, [
+                'price' => $parts['price'],
+                'active' => true,
+            ]) ?? 0;
+        }
+
         return ProductPriceService::adjustedTotal(
             $parts['price'],
             $parts['profit'],