refactor(components): extract shared entity utilities and simplify item components (F1.3, F1.4)

Extract 3 entity composables (useEntityCustomFields, useEntityDocuments,
useEntityProductDisplay) and entityCustomFieldLogic utility shared across
ComponentItem (1336→585 LOC) and PieceItem (1588→740 LOC).
Improve type safety in edit/create pages with explicit casts.

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

app/composables/useEntityProductDisplay.ts

@@ -0,0 +1,103 @@
+/**
+ * Reactive product display for entity items (ComponentItem, PieceItem).
+ *
+ * Resolves product information from entity.product, entity.__productDisplay,
+ * or a selectedProduct ref, and produces display-ready computed properties.
+ */
+
+import { computed, type Ref } from 'vue'
+
+const currencyFormatter = new Intl.NumberFormat('fr-FR', {
+  style: 'currency',
+  currency: 'EUR',
+  currencyDisplay: 'narrowSymbol',
+})
+
+function buildProductDisplay(product: any) {
+  if (!product || typeof product !== 'object') return null
+
+  const suppliers = Array.isArray(product.constructeurs)
+    ? product.constructeurs
+        .map((c: any) => c?.name)
+        .filter((name: any) => typeof name === 'string' && name.trim().length > 0)
+        .join(', ')
+    : product.supplierLabel || null
+
+  const priceValue = product.supplierPrice ?? product.price ?? product.priceLabel ?? product.priceDisplay ?? null
+  let price: string | null = null
+  if (priceValue !== null && priceValue !== undefined) {
+    const parsed = Number(priceValue)
+    if (!Number.isNaN(parsed)) {
+      price = currencyFormatter.format(parsed)
+    } else if (typeof priceValue === 'string' && priceValue.trim().length > 0) {
+      price = priceValue
+    }
+  }
+
+  return {
+    name: product.name || product.label || product.reference || product.productName || null,
+    reference: product.reference || null,
+    category: product.typeProduct?.name || product.category || null,
+    suppliers,
+    price,
+  }
+}
+
+export interface EntityProductDisplayDeps {
+  entity: () => any
+  selectedProduct?: Ref<any>
+}
+
+export function useEntityProductDisplay(deps: EntityProductDisplayDeps) {
+  const { entity, selectedProduct } = deps
+
+  const displayProduct = computed(() => {
+    // Priority: selectedProduct (for PieceItem) → entity.product → entity.__productDisplay
+    if (selectedProduct?.value) {
+      const normalized = buildProductDisplay(selectedProduct.value)
+      if (normalized) return normalized
+    }
+    const explicit = entity().product || null
+    const normalized = buildProductDisplay(explicit)
+    if (normalized) return normalized
+    const fallback = entity().__productDisplay
+    if (fallback) {
+      return {
+        name: fallback.name || null,
+        reference: fallback.reference || null,
+        category: fallback.category || null,
+        suppliers: fallback.suppliers || null,
+        price: fallback.price || null,
+      }
+    }
+    return null
+  })
+
+  const displayProductName = computed(() => {
+    if (displayProduct.value?.name) return displayProduct.value.name
+    const e = entity()
+    return e.product?.name || e.productName || e.productLabel || null
+  })
+
+  const productInfoRows = computed(() => {
+    if (!displayProduct.value) return []
+    const rows: { label: string; value: string }[] = []
+    if (displayProduct.value.reference) rows.push({ label: 'Référence', value: displayProduct.value.reference })
+    if (displayProduct.value.price) rows.push({ label: 'Prix indicatif', value: displayProduct.value.price })
+    if (displayProduct.value.suppliers) rows.push({ label: 'Fournisseur(s)', value: displayProduct.value.suppliers })
+    if (displayProduct.value.category) rows.push({ label: 'Catégorie', value: displayProduct.value.category })
+    return rows
+  })
+
+  const productDocuments = computed(() => {
+    const product = selectedProduct?.value || entity().product || null
+    return Array.isArray(product?.documents) ? product.documents : []
+  })
+
+  return {
+    displayProduct,
+    displayProductName,
+    productInfoRows,
+    productDocuments,
+  }
+}