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/ports/folder_ports.rs

@@ -96,16 +96,6 @@ pub trait FolderUseCase: Send + Sync + 'static {
     /// Deletes a folder (ownership verified against caller_id)
     async fn delete_folder_with_perms(&self, id: &str, caller_id: Uuid) -> Result<(), DomainError>;
 
-    /// Creates a root-level home folder for a user during registration.
-    /// `drive_id` is the user's personal drive; the wrapper folder stays
-    /// during the D0 dual-write window (retires in M2b later).
-    async fn create_home_folder(
-        &self,
-        user_id: Uuid,
-        drive_id: Uuid,
-        name: String,
-    ) -> Result<FolderDto, DomainError>;
-
     /// Lists every folder in a subtree rooted at `folder_id` (inclusive),
     /// ordered by path.  Uses ltree `<@` — single GiST-indexed query.
     ///

src/application/ports/user_lifecycle.rs

@@ -127,7 +127,7 @@ pub enum LogoutReason {
 
 /// How aggressively `on_user_deleted` cleanup should run. Today both
 /// variants are equivalent (only `AuditLifecycleHook` exists, and it logs
-/// regardless). The split exists so PR 4's `HomeFolderLifecycleHook` can
+/// regardless). The split exists so PR 4's `PersonalDriveLifecycleHook` can
 /// trash on `AdminDelete` but hard-delete on `GdprPurge`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum DeletionMode {