feat(drive): improve Drive model

now Drive is purely a metadata
    each drive has always a root folder
    this model minimize Oxicloud changes, and simplify
    the Drive name is simply the folder's root's name
    note: owner of Drive has more permission that an owner of the root folder

src/application/services/search_service.rs

@@ -306,7 +306,7 @@ impl SearchService {
             .list_for_subjects(&subject_types, &subject_ids)
             .await
         {
-            Ok(drives) => drives.into_iter().map(|d| d.id).collect(),
+            Ok(drives) => drives.into_iter().map(|d| d.drive.id).collect(),
             Err(e) => {
                 tracing::warn!("Content-index: drive lookup failed — degrading to empty: {e}");
                 return Vec::new();