refactor(create_folder): add an ownership check while creating a folder + refactor code

src/interfaces/api/handlers/folder_handler.rs

@@ -76,25 +76,7 @@ impl FolderHandler {
             }
         }
 
-        // ── SECURITY: Verify parent folder ownership (IDOR V-04 fix) ──
-        if let Some(ref parent_id) = dto.parent_id {
-            use crate::application::ports::inbound::FolderUseCase;
-            if service
-                .get_folder_owned(parent_id, auth_user.id)
-                .await
-                .is_err()
-            {
-                tracing::warn!(
-                    "create_folder: user '{}' attempted to create folder in parent '{}' owned by another user",
-                    auth_user.username,
-                    parent_id,
-                );
-                return AppError::not_found(format!("Parent folder not found: {}", parent_id))
-                    .into_response();
-            }
-        }
-
-        match service.create_folder(dto).await {
+        match service.create_folder(dto, auth_user.id).await {
             Ok(folder) => (StatusCode::CREATED, Json(folder)).into_response(),
             Err(err) => AppError::from(err).into_response(),
         }