refactor(frontend) : extract shared components and reduce file sizes

- Extract CustomFieldInputGrid.vue from 6 duplicated template blocks (~70 lines each)
- Extract EntityHistorySection.vue from 3 identical history sections in edit pages
- Extract useDragReorder composable from 4 identical drag-and-drop implementations in StructureNodeEditor (~330 lines → ~30)
- Extract catalogDisplayUtils.ts (resolvePrimaryDocument, resolveSupplierNames, buildSuppliersDisplay)
- Remove redundant computed wrappers (historyEntries, loadingTypes, selectedFiles)
- Remove unused imports (fieldKey, historyActionLabel, formatHistoryDate, *HistoryEntry types)
- Move Intl.DateTimeFormat to module-level in date.ts

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

app/components/DocumentUpload.vue

@@ -130,7 +130,7 @@ const cleanupRemovedPreviews = (previousFiles = [], nextFiles = []) => {
   })
 }
 
-const selectedFiles = computed(() => internalFiles.value)
+const selectedFiles = internalFiles
 
 watch(
   () => props.modelValue,