refactor(custom-fields) : unify 3 parallel implementations into 1 module

Replace ~2900 lines across 9 files with ~400 lines in 2 files:
- shared/utils/customFields.ts (types + pure helpers)
- composables/useCustomFieldInputs.ts (reactive composable)

Migrated all consumers:
- Backend: add defaultValue to API Platform serialization groups
- Standalone pages: component edit/create, piece edit/create, product edit/create/detail
- Machine page: MachineCustomFieldsCard, MachineInfoCard, useMachineDetailCustomFields
- Hierarchy: ComponentItem, PieceItem
- Shared: CustomFieldDisplay, CustomFieldInputGrid
- Category editor: componentStructure.ts

Deleted:
- entityCustomFieldLogic.ts (335 lines)
- customFieldUtils.ts (440 lines)
- customFieldFormUtils.ts (404 lines)
- useEntityCustomFields.ts (181 lines)
- customFieldFormUtils.test.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/app/composables/useComponentEdit.ts

@@ -6,7 +6,6 @@ import { usePieceTypes } from '~/composables/usePieceTypes'
 import { useProductTypes } from '~/composables/useProductTypes'
 import { usePieces } from '~/composables/usePieces'
 import { useProducts } from '~/composables/useProducts'
-import { useCustomFields } from '~/composables/useCustomFields'
 import { useApi } from '~/composables/useApi'
 import { useToast } from '~/composables/useToast'
 import { extractRelationId } from '~/shared/apiRelations'
@@ -29,12 +28,7 @@ import {
 import type { ComponentModelStructure } from '~/shared/types/inventory'
 import type { ModelType } from '~/services/modelTypes'
 import { canPreviewDocument } from '~/utils/documentPreview'
-import {
-  type CustomFieldInput,
-  buildCustomFieldInputs,
-  requiredCustomFieldsFilled as _requiredCustomFieldsFilled,
-  saveCustomFieldValues as _saveCustomFieldValues,
-} from '~/shared/utils/customFieldFormUtils'
+import { useCustomFieldInputs, type CustomFieldInput } from '~/composables/useCustomFieldInputs'
 import { collectStructureSelections } from '~/shared/utils/structureSelectionUtils'
 
 interface ComponentCatalogType extends ModelType {
@@ -64,7 +58,6 @@ export function useComponentEdit(componentId: string) {
   const { products } = useProducts()
   const { ensureConstructeurs } = useConstructeurs()
   const { fetchLinks, syncLinks } = useConstructeurLinks()
-  const { upsertCustomFieldValue, updateCustomFieldValue } = useCustomFields()
   const toast = useToast()
   const { loadDocumentsByComponent, uploadDocuments, deleteDocument } = useDocuments()
   const {
@@ -96,7 +89,23 @@ export function useComponentEdit(componentId: string) {
   const originalConstructeurLinks = ref<ConstructeurLinkEntry[]>([])
   const constructeurIdsFromForm = computed(() => constructeurIdsFromLinks(constructeurLinks.value))
 
-  const customFieldInputs = ref<CustomFieldInput[]>([])
+  const {
+    fields: customFieldInputs,
+    requiredFilled: requiredCustomFieldsFilled,
+    saveAll: saveAllCustomFields,
+    refresh: refreshCustomFieldInputs,
+  } = useCustomFieldInputs({
+    definitions: computed(() => selectedTypeStructure.value?.customFields ?? []),
+    values: computed(() => component.value?.customFieldValues ?? []),
+    entityType: 'composant',
+    entityId: computed(() => component.value?.id ?? null),
+    onValueCreated: (newValue) => {
+      if (component.value && Array.isArray(component.value.customFieldValues)) {
+        component.value.customFieldValues.push(newValue)
+      }
+    },
+  })
+
   const fetchedPieceTypeMap = ref<Record<string, string>>({})
   const pieceTypeLabelMap = computed(() =>
     buildTypeLabelMap(pieceTypes.value, fetchedPieceTypeMap.value),
@@ -207,19 +216,6 @@ export function useComponentEdit(componentId: string) {
     return structure ? normalizeStructureForEditor(structure) : null
   })
 
-  const refreshCustomFieldInputs = (
-    structureOverride?: ComponentModelStructure | null,
-    valuesOverride?: any[] | null,
-  ) => {
-    const structure = structureOverride ?? selectedTypeStructure.value ?? null
-    const values = valuesOverride ?? component.value?.customFieldValues ?? null
-    customFieldInputs.value = buildCustomFieldInputs(structure, values)
-  }
-
-  const requiredCustomFieldsFilled = computed(() =>
-    _requiredCustomFieldsFilled(customFieldInputs.value),
-  )
-
   const canSubmit = computed(() => Boolean(
     canEdit.value
     && component.value
@@ -239,8 +235,7 @@ export function useComponentEdit(componentId: string) {
       component.value = result.data
       componentDocuments.value = Array.isArray(result.data?.documents) ? result.data.documents : []
 
-      const customValues = Array.isArray(result.data?.customFieldValues) ? result.data.customFieldValues : []
-      refreshCustomFieldInputs(undefined, customValues)
+      // The watcher on useCustomFieldInputs will auto-refresh when component.value changes
 
       loadHistory(result.data.id).catch(() => {})
     }
@@ -392,14 +387,10 @@ export function useComponentEdit(componentId: string) {
       const result = await updateComposant(component.value.id, payload)
       if (result.success && result.data) {
         const updatedComponent = result.data as Record<string, any>
-        await _saveCustomFieldValues(
-          'composant',
-          updatedComponent.id,
-          [
-            updatedComponent?.typeComposant?.structure?.customFields,
-          ],
-          { customFieldInputs, upsertCustomFieldValue, updateCustomFieldValue, toast },
-        )
+        const failedFields = await saveAllCustomFields()
+        if (failedFields.length) {
+          toast.showError(`Erreur sur les champs : ${failedFields.join(', ')}`)
+        }
 
         // Save slot edits
         const slotPromises: Promise<any>[] = []
@@ -499,7 +490,7 @@ export function useComponentEdit(componentId: string) {
         initialized.value = true
       }
 
-      refreshCustomFieldInputs(selectedTypeStructure.value ?? currentStructure, currentComponent.customFieldValues)
+      // useCustomFieldInputs auto-refreshes via its watcher on definitions + values
     },
     { immediate: true },
   )