feat(08-07): create domain modules admin.js, folders.js, shares.js, cloud.js — CODE-04

- admin.js: 17 functions; adminExportAuditLogCsv + adminDownloadDailyExport use fetchWithRetry
- folders.js: 6 functions — import request from utils.js
- shares.js: 5 functions — import request from utils.js
- cloud.js: 7 functions including initiateOAuth — import request from utils.js
- Blob-download retry boilerplate eliminated from admin.js (CODE-08)

frontend/src/api/folders.js

@@ -0,0 +1,46 @@
+/**
+ * Folders API — listing, creation, renaming, deletion, document moves.
+ *
+ * Consumers: stores/folders.js, FolderTreeItem.vue, AppSidebar.vue
+ */
+
+import { request } from './utils.js'
+
+export function listFolders(parentId = null) {
+  const params = new URLSearchParams()
+  if (parentId != null) params.set('parent_id', parentId)
+  const qs = params.toString()
+  return request(`/api/folders${qs ? `?${qs}` : ''}`)
+}
+
+export function createFolder(name, parentId = null) {
+  return request('/api/folders', {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ name, parent_id: parentId || null }),
+  })
+}
+
+export function getFolder(folderId) {
+  return request(`/api/folders/${folderId}`)
+}
+
+export function renameFolder(folderId, name) {
+  return request(`/api/folders/${folderId}`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ name }),
+  })
+}
+
+export function deleteFolder(folderId) {
+  return request(`/api/folders/${folderId}`, { method: 'DELETE' })
+}
+
+export function moveDocument(docId, folderId) {
+  return request(`/api/documents/${docId}/folder`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ folder_id: folderId || null }),
+  })
+}