refactor(inventory): update stock validation rules and enforce stock_difference requirement

app/Domains/Ticketing/FiestaFutbolInfantil/Services/AccommodationService.php

@@ -169,7 +169,7 @@ class AccommodationService
             'title' => trim($variant['title']),
             'value' => $this->valueCode($variant['title']),
             'description' => $variant['description'] ?? null,
-            'stock' => (int) $variant['stock'],
+            ...(array_key_exists('stock', $variant) ? ['stock' => (int) $variant['stock']] : []),
         ])->all();
     }
 
@@ -257,8 +257,10 @@ class AccommodationService
             'descripcion' => $data['description'],
             'precio' => $data['price'],
         ]);
-        $stockDifference = (int) ($data['stock_difference'] ?? ($data['stock'] - $inventory->availableStock()));
-        $inventory->adjustAvailableStock($stockDifference, idempotencyKey: $stockAdjustmentId);
+        $inventory->adjustAvailableStock(
+            (int) $data['stock_difference'],
+            idempotencyKey: $stockAdjustmentId,
+        );
         $variant->definitions()->updateOrCreate(
             ['item_attribute_id' => $itemAttribute->id],
             ['value' => $data['value']],