feat(composant) : add virtual getStructure() rebuilding legacy JSON from slot tables

Exposes structure as a computed property from pieceSlots, productSlots,
and subcomponentSlots relations, including slotId for frontend quantity
persistence.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Entity/Composant.php

@@ -337,6 +337,59 @@ class Composant
         return $this->productSlots;
     }
 
+    /**
+     * Virtual property — rebuilds the legacy structure JSON from slot tables.
+     *
+     * @return null|array{pieces: list<array<string, mixed>>, products: list<array<string, mixed>>, subcomponents: list<array<string, mixed>>}
+     */
+    #[Groups(['composant:read'])]
+    public function getStructure(): ?array
+    {
+        $pieces = [];
+        foreach ($this->pieceSlots as $slot) {
+            $pieces[] = [
+                'slotId'          => $slot->getId(),
+                'typePieceId'     => $slot->getTypePiece()?->getId(),
+                'selectedPieceId' => $slot->getSelectedPiece()?->getId(),
+                'quantity'        => $slot->getQuantity(),
+                'position'        => $slot->getPosition(),
+            ];
+        }
+
+        $products = [];
+        foreach ($this->productSlots as $slot) {
+            $products[] = [
+                'slotId'            => $slot->getId(),
+                'typeProductId'     => $slot->getTypeProduct()?->getId(),
+                'selectedProductId' => $slot->getSelectedProduct()?->getId(),
+                'familyCode'        => $slot->getFamilyCode(),
+                'position'          => $slot->getPosition(),
+            ];
+        }
+
+        $subcomponents = [];
+        foreach ($this->subcomponentSlots as $slot) {
+            $subcomponents[] = [
+                'slotId'              => $slot->getId(),
+                'alias'               => $slot->getAlias(),
+                'familyCode'          => $slot->getFamilyCode(),
+                'typeComposantId'     => $slot->getTypeComposant()?->getId(),
+                'selectedComponentId' => $slot->getSelectedComposant()?->getId(),
+                'position'            => $slot->getPosition(),
+            ];
+        }
+
+        if (empty($pieces) && empty($products) && empty($subcomponents)) {
+            return null;
+        }
+
+        return [
+            'pieces'        => $pieces,
+            'products'      => $products,
+            'subcomponents' => $subcomponents,
+        ];
+    }
+
     public function addProductSlot(ComposantProductSlot $productSlot): static
     {
         if (!$this->productSlots->contains($productSlot)) {