feat(drive): remove create_home_folder

remove create_home_folder() & ensure_home_folder()

    now: on_user_created() and on_user_login both() call provision_if_needed()
    which calls **create_personal_drive_atomic()**

    add a helper to find Personal drive for a user and also it's root directorry

src/application/services/user_lifecycle_service.rs

@@ -132,7 +132,7 @@ impl UserLifecycleService {
 //
 // Always-on observer. Emits one structured `tracing::info!(target: "audit",
 // ...)` line per event. The only hook registered in PR 1; subsequent PRs
-// add HomeFolderLifecycleHook, AuthzCacheLifecycleHook, etc., each living
+// add PersonalDriveLifecycleHook, AuthzCacheLifecycleHook, etc., each living
 // next to the service it works for.
 // ─────────────────────────────────────────────────────────────────────────────