fix(10): resolve WR-03/WR-04 code review warnings

WR-04: AdminAuditView.vue had a local formatTimestamp() duplicating shared
util logic — moved to utils/formatters.js and imported from there per CLAUDE.md
shared-module rule.

WR-03: Remove unused onUnmounted import from FileManagerView.vue.

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

frontend/src/utils/formatters.js

@@ -18,6 +18,16 @@ export function formatSize(bytes) {
   return (bytes / 1048576).toFixed(1) + ' MB'
 }
 
+/** Formats an ISO timestamp for audit log display: YYYY-MM-DD HH:MM:SS */
+export function formatTimestamp(iso) {
+  if (!iso) return '—'
+  try {
+    return new Date(iso).toISOString().replace('T', ' ').slice(0, 19)
+  } catch {
+    return iso
+  }
+}
+
 /** Maps a cloud provider slug to a Tailwind text-color class. */
 export function providerColor(provider) {
   const map = {

frontend/src/views/FileManagerView.vue

@@ -44,7 +44,7 @@
 </template>
 
 <script setup>
-import { ref, reactive, computed, watch, onMounted, onUnmounted } from 'vue'
+import { ref, reactive, computed, watch, onMounted } from 'vue'
 import { useRoute, useRouter } from 'vue-router'
 import { useFoldersStore } from '../stores/folders.js'
 import { useDocumentsStore } from '../stores/documents.js'

frontend/src/views/admin/AdminAuditView.vue

@@ -200,6 +200,7 @@ import { ref, reactive, onMounted, computed } from 'vue'
 import * as api from '../../api/client.js'
 import BreadcrumbBar from '../../components/ui/BreadcrumbBar.vue'
 import EmptyState from '../../components/ui/EmptyState.vue'
+import { formatTimestamp } from '../../utils/formatters.js'
 
 const entries = ref([])
 const total = ref(0)
@@ -332,14 +333,6 @@ async function downloadDailyExport() {
   }
 }
 
-function formatTimestamp(iso) {
-  if (!iso) return '—'
-  try {
-    return new Date(iso).toISOString().replace('T', ' ').slice(0, 19)
-  } catch {
-    return iso
-  }
-}
 
 function actionTypeClass(eventType) {
   if (!eventType) return 'bg-gray-100 text-gray-600'