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/useEntityDocuments.ts

@@ -0,0 +1,122 @@
+/**
+ * Reactive document management for entity items (ComponentItem, PieceItem).
+ *
+ * Handles document CRUD operations, preview modal state, and lazy loading.
+ * Display helpers (formatSize, shouldInlinePdf, etc.) are imported from
+ * shared/utils/documentDisplayUtils.ts.
+ */
+
+import { ref, computed, watch } from 'vue'
+import { useDocuments } from '~/composables/useDocuments'
+import { canPreviewDocument } from '~/utils/documentPreview'
+
+export interface EntityDocumentsDeps {
+  entity: () => any
+  entityType: 'composant' | 'piece'
+}
+
+export function useEntityDocuments(deps: EntityDocumentsDeps) {
+  const { entity, entityType } = deps
+  const { uploadDocuments, deleteDocument } = useDocuments()
+
+  const loadDocumentsFn = entityType === 'composant'
+    ? useDocuments().loadDocumentsByComponent
+    : useDocuments().loadDocumentsByPiece
+
+  const selectedFiles = ref<File[]>([])
+  const uploadingDocuments = ref(false)
+  const loadingDocuments = ref(false)
+  const documentsLoaded = ref(!!(entity().documents && entity().documents.length))
+
+  const documents = computed(() => entity().documents || [])
+
+  // Preview modal state
+  const previewDocument = ref<any>(null)
+  const previewVisible = ref(false)
+
+  const openPreview = (doc: any) => {
+    if (!canPreviewDocument(doc)) return
+    previewDocument.value = doc
+    previewVisible.value = true
+  }
+
+  const closePreview = () => {
+    previewVisible.value = false
+    previewDocument.value = null
+  }
+
+  // Document watchers
+  watch(
+    () => entity().documents,
+    (docs: any) => {
+      documentsLoaded.value = !!(docs && docs.length)
+    },
+  )
+
+  // CRUD operations
+  const refreshDocuments = async () => {
+    const e = entity()
+    if (!e?.id) return
+    loadingDocuments.value = true
+    try {
+      const result: any = await loadDocumentsFn(e.id, { updateStore: false })
+      if (result.success) {
+        e.documents = result.data || []
+        documentsLoaded.value = true
+      }
+    } finally {
+      loadingDocuments.value = false
+    }
+  }
+
+  const ensureDocumentsLoaded = async () => {
+    if (documentsLoaded.value || !entity()?.id) return
+    await refreshDocuments()
+  }
+
+  const handleFilesAdded = async (files: File[]) => {
+    const e = entity()
+    if (!files.length || !e?.id) return
+    uploadingDocuments.value = true
+    try {
+      const contextKey = entityType === 'composant' ? 'composantId' : 'pieceId'
+      const result: any = await uploadDocuments(
+        { files, context: { [contextKey]: e.id } } as any,
+        { updateStore: false } as any,
+      )
+      if (result.success) {
+        const newDocs = result.data || []
+        e.documents = [...newDocs, ...(e.documents || [])]
+        documentsLoaded.value = true
+        selectedFiles.value = []
+      }
+    } finally {
+      uploadingDocuments.value = false
+    }
+  }
+
+  const removeDocument = async (documentId: string) => {
+    if (!documentId) return
+    const result: any = await deleteDocument(documentId, { updateStore: false } as any)
+    if (result.success) {
+      const e = entity()
+      e.documents = (e.documents || []).filter((doc: any) => doc.id !== documentId)
+    }
+  }
+
+  return {
+    documents,
+    selectedFiles,
+    uploadingDocuments,
+    loadingDocuments,
+    documentsLoaded,
+    previewDocument,
+    previewVisible,
+    openPreview,
+    closePreview,
+    refreshDocuments,
+    ensureDocumentsLoaded,
+    handleFilesAdded,
+    removeDocument,
+  }
+}