feat: Add product dependencies (requirements and exclusions) to database, admin UI and wizard validation

shop/lib/actions/orders.ts

@@ -104,6 +104,38 @@ export async function submitOrder(params: {
     }
   }
 
+  // Product-level constraints validation
+  const selectedProductIds = Object.values(selections)
+    .map(s => s.productId)
+    .filter((id): id is string => !!id)
+
+  for (const prodId of selectedProductIds) {
+    const prod = dbProducts.find(p => p.id === prodId)
+    if (!prod) continue
+
+    // Product requirements check
+    if (prod.requirements && prod.requirements.length > 0) {
+      const missing = prod.requirements.filter(reqId => !selectedProductIds.includes(reqId))
+      if (missing.length > 0) {
+        const missingNames = missing
+          .map(reqId => dbProducts.find(p => p.id === reqId)?.name || reqId)
+          .join(', ')
+        throw new Error(`Das Produkt "${prod.name}" erfordert die Auswahl von: ${missingNames}.`)
+      }
+    }
+
+    // Product exclusions check
+    if (prod.exclusions && prod.exclusions.length > 0) {
+      const conflicting = prod.exclusions.filter(exId => selectedProductIds.includes(exId))
+      if (conflicting.length > 0) {
+        const conflictingNames = conflicting
+          .map(exId => dbProducts.find(p => p.id === exId)?.name || exId)
+          .join(', ')
+        throw new Error(`Das Produkt "${prod.name}" schließt die gleichzeitige Auswahl von folgenden Produkten aus: ${conflictingNames}.`)
+      }
+    }
+  }
+
   // 1. Snapshots aufbauen
   // Wenn Endkunde vorhanden: dessen Daten einfrieren; sonst Partner-Profil (Fallback)
   const customerSnapshot = buildCustomerSnapshot(customerProfile, endCustomer ?? null)