Function transfer_retry 

pub async fn transfer_retry(
    request_id: String,
    queue: State<'_, TransferQueueHandle>,
    pool: State<'_, S3ClientPoolHandle>,
    locks: State<'_, LockRegistryHandle>,
    store: State<'_, ProfileStoreHandle>,
    multipart_table: State<'_, MultipartTableHandle>,
    log: State<'_, NotificationLogHandle>,
    settings: State<'_, SettingsHandle>,
    channel: AppHandle,
) -> Result<String, AppError>

Re-enqueue a failed or canceled transfer from the beginning.

The original transfer record is not mutated. A fresh request_id is returned. This satisfies AC-14: “the transfer restarts from the beginning (not resumable in v1)”.