feat(phase-4-09): create new components — FolderRow, FolderBreadcrumb, FolderDeleteModal, ShareModal, DocumentPreviewModal, SearchBar, SortControls, AuditLogTab

- FolderRow: inline rename, three-dot menu, delete/rename callbacks, outside-click close
- FolderBreadcrumb: truncation at depth > 4, nav aria-label, ol structure
- FolderDeleteModal: role=dialog, warning icon, doc count in body, Keep/Delete buttons
- ShareModal: handle input, recipients list with revoke, 404/409 error handling
- DocumentPreviewModal: iframe with proxy URL only (never presigned), Escape/overlay close
- SearchBar: role=search, aria-label, Escape clears
- SortControls: aria-pressed, direction indicator, toggle vs switch logic
- AuditLogTab: filters, paginated table, CSV export via window.location.href
- api/client.js: add adminListAuditLog function

frontend/src/api/client.js

@@ -345,6 +345,19 @@ export function updateMyPreferences(payload) {
   })
 }
 
+// ── Audit Log ─────────────────────────────────────────────────────────────────
+
+export function adminListAuditLog({ start, end, user_id, event_type, page = 1, per_page = 50 } = {}) {
+  const params = new URLSearchParams()
+  if (start) params.set('start', start)
+  if (end) params.set('end', end)
+  if (user_id) params.set('user_id', user_id)
+  if (event_type) params.set('event_type', event_type)
+  params.set('page', page)
+  params.set('per_page', per_page)
+  return request(`/api/admin/audit-log?${params}`)
+}
+
 // ── Document content proxy URL ────────────────────────────────────────────────
 
 export function getDocumentContentUrl(docId) {