refactor(checkout): materialize purchase items on confirmation

app/Domains/Purchase/Models/Purchase.php

@@ -4,6 +4,7 @@ namespace App\Domains\Purchase\Models;
 
 use App\Domains\Auth\Models\User;
 use App\Domains\Cart\Models\Cart;
+use App\Domains\Catalog\Models\StockReservation;
 use App\Domains\Logging\Models\Concerns\LogsValueChanges;
 use App\Domains\Purchase\Events\PurchasePaid;
 use App\Domains\Tenant\Models\Tenant;
@@ -116,6 +117,12 @@ class Purchase extends Model
         return $this->hasMany(Ticket::class, 'source_purchase_id');
     }
 
+    /** @return HasMany<StockReservation, $this> */
+    public function stockReservations(): HasMany
+    {
+        return $this->hasMany(StockReservation::class);
+    }
+
     /**
      * @return HasOne<TelepagosQr, $this>
      */
@@ -143,11 +150,16 @@ class Purchase extends Model
 
     public function calculateCurrentTotalAmount(): float
     {
-        if ($this->relationLoaded('items')) {
+        if ($this->relationLoaded('items') && $this->getRelation('items')->isNotEmpty()) {
             return (float) $this->getRelation('items')->sum('total');
         }
 
-        return (float) $this->items()->sum('total');
+        $itemsTotal = (float) $this->items()->sum('total');
+        if ($itemsTotal > 0 || $this->items()->exists()) {
+            return $itemsTotal;
+        }
+
+        return (float) ($this->cart?->getTotalAmount() ?? $this->total ?? 0);
     }
 
     protected function valueChangeTenantCode(): string