fix(piece) : persist slot quantity on blur and send prix as string

- Save composant piece slot quantity via PATCH on blur
- Pass slotId through hierarchy and selection entries
- Send prix as string (not number) to match backend expectation
- Show quantity in view mode when > 1
- Allow quantity edit for all pieces (not just root-level)

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

app/composables/useMachineDetailUpdates.ts

@@ -110,18 +110,18 @@ export function useMachineDetailUpdates(deps: UseMachineDetailUpdatesDeps) {
       const productId = updatedComponent.productId
         ? String(updatedComponent.productId)
         : null
-      const prix =
+      const prixStr =
         updatedComponent.prix !== null &&
         updatedComponent.prix !== undefined &&
         String(updatedComponent.prix).trim() !== ''
-          ? Number(updatedComponent.prix)
+          ? String(updatedComponent.prix)
           : null
 
       const result: any = await updateComposantApi(updatedComponent.id as string, {
         name: updatedComponent.name,
         reference: updatedComponent.reference,
         constructeurIds: cIds,
-        prix: Number.isNaN(prix) ? null : prix,
+        prix: prixStr,
         productId,
       } as any)
       if (result.success) {
@@ -140,18 +140,18 @@ export function useMachineDetailUpdates(deps: UseMachineDetailUpdatesDeps) {
       updatedPiece.constructeur,
     )
     const productId = updatedPiece.productId ? String(updatedPiece.productId) : null
-    const prix =
+    const prixStr =
       updatedPiece.prix !== null &&
       updatedPiece.prix !== undefined &&
       String(updatedPiece.prix).trim() !== ''
-        ? Number(updatedPiece.prix)
+        ? String(updatedPiece.prix)
         : null
 
     const result: any = await updatePieceApi(updatedPiece.id as string, {
       name: updatedPiece.name,
       reference: updatedPiece.reference || null,
       constructeurIds: cIds,
-      prix: Number.isNaN(prix) ? null : prix,
+      prix: prixStr,
       productId,
     } as any)
     if (result.success) {
@@ -181,6 +181,13 @@ export function useMachineDetailUpdates(deps: UseMachineDetailUpdatesDeps) {
           )
         }
       }
+
+      // Update slot quantity if this is a composant structure piece
+      const slotId = updatedPiece.slotId as string | null
+      const quantity = typeof updatedPiece.quantity === 'number' ? Math.max(1, updatedPiece.quantity) : null
+      if (slotId && quantity !== null) {
+        await apiPatch(`/composant-piece-slots/${slotId}`, { quantity })
+      }
     } catch (error) {
       console.error('Erreur lors de la mise à jour de la pièce:', error)
     }