feat(perms): add documents.manage_folders permission

Mirrors files.manage_folders. Gates create / rename / move / delete
of document folders, plus moving documents between folders. Reps with
documents.edit but not manage_folders can rename docs in place but
can't reorganise the tree. Admin + sales_manager get the perm by
default; sales_rep + viewer don't.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/admin/roles/role-form.tsx

@@ -39,6 +39,7 @@ const DEFAULT_PERMISSIONS: Record<string, Record<string, boolean>> = {
     send_for_signing: false,
     upload_signed: false,
     delete: false,
+    manage_folders: false,
   },
   expenses: {
     view: false,