fix(machines) : pièce supprimée ne bloque plus la machine

Un lien machine_piece_links orphelin (pieceid pointant vers une pièce
supprimée) faisait charger les documents via l'id du lien
(GET /documents/piece/{linkId}) → 404 + toast bloquant, et la catégorie
restait affichée à vide.

- front : useEntityDocuments ne charge plus les documents pour un node
  pending (refreshDocuments + ensureDocumentsLoaded) + test
- back : migration Version20260529150000 réparant les 2 FK CASCADE vers
  pieces (fk_mpl_piece, fk_cfv_piece) jamais appliquées par
  Version20260528090000, avec nettoyage des orphelins (1 mpl + 3 cfv)

frontend/app/composables/useEntityDocuments.ts

@@ -56,7 +56,9 @@ export function useEntityDocuments(deps: EntityDocumentsDeps) {
   // CRUD operations
   const refreshDocuments = async () => {
     const e = entity()
-    if (!e?.id || e._structurePiece) return
+    // Pending / category-only nodes carry the link id (not a real entity id) and
+    // have no backing piece/composant — never request documents for them.
+    if (!e?.id || e._structurePiece || e.pendingEntity) return
     loadingDocuments.value = true
     try {
       const result: any = await loadDocumentsFn(e.id, { updateStore: false })
@@ -70,7 +72,8 @@ export function useEntityDocuments(deps: EntityDocumentsDeps) {
   }
 
   const ensureDocumentsLoaded = async () => {
-    if (documentsLoaded.value || !entity()?.id) return
+    const e = entity()
+    if (documentsLoaded.value || !e?.id || e.pendingEntity) return
     await refreshDocuments()
   }
 

frontend/tests/composables/useEntityDocuments.test.ts

@@ -0,0 +1,73 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+import { useEntityDocuments } from '~/composables/useEntityDocuments'
+
+// ---------------------------------------------------------------------------
+// Mocks
+// ---------------------------------------------------------------------------
+
+const mockLoadDocumentsByPiece = vi.fn()
+const mockLoadDocumentsByComponent = vi.fn()
+
+vi.mock('~/composables/useDocuments', () => ({
+  useDocuments: () => ({
+    loadDocumentsByPiece: mockLoadDocumentsByPiece,
+    loadDocumentsByComponent: mockLoadDocumentsByComponent,
+    uploadDocuments: vi.fn(),
+    deleteDocument: vi.fn(),
+    updateDocument: vi.fn(),
+  }),
+}))
+
+vi.mock('~/utils/documentPreview', () => ({
+  canPreviewDocument: () => true,
+}))
+
+beforeEach(() => {
+  vi.clearAllMocks()
+})
+
+// ---------------------------------------------------------------------------
+// refreshDocuments — pending / orphan entities
+// ---------------------------------------------------------------------------
+describe('refreshDocuments', () => {
+  it('does NOT load documents for a pending piece node (orphan link id is not a piece id)', async () => {
+    // A category-only / pending piece node: its `id` is the machinePieceLink id,
+    // there is no real piece behind it (pieceId is null).
+    const pendingNode = {
+      id: 'cl48179803369dd93b4a90b784', // machinePieceLink id, NOT a piece id
+      pieceId: null,
+      pendingEntity: true,
+      documents: [],
+    }
+
+    const { refreshDocuments } = useEntityDocuments({
+      entity: () => pendingNode,
+      entityType: 'piece',
+    })
+
+    await refreshDocuments()
+
+    expect(mockLoadDocumentsByPiece).not.toHaveBeenCalled()
+  })
+
+  it('loads documents for a real piece node using its piece id', async () => {
+    mockLoadDocumentsByPiece.mockResolvedValue({ success: true, data: [] })
+
+    const realNode = {
+      id: 'clrealpieceid000000000000',
+      pieceId: 'clrealpieceid000000000000',
+      pendingEntity: false,
+      documents: [],
+    }
+
+    const { refreshDocuments } = useEntityDocuments({
+      entity: () => realNode,
+      entityType: 'piece',
+    })
+
+    await refreshDocuments()
+
+    expect(mockLoadDocumentsByPiece).toHaveBeenCalledWith('clrealpieceid000000000000', { updateStore: false })
+  })
+})