Introduce new environment variables to control the behavior of one-time download boxes:
- `WARPBOX_ONE_TIME_DOWNLOAD_EXPIRY_SECONDS`: Sets the lifetime of a one-time box after uploads are complete.
- `WARPBOX_ONE_TIME_DOWNLOAD_RETRY_ON_FAILURE`: Determines whether a box remains available if the ZIP creation or transfer fails.
To support these settings, the ZIP delivery process was refactored to use a temporary file. This ensures that a one-time box is only marked as consumed after the file has been successfully transferred to the client, preventing data loss on network interruptions.
Additionally, added a `DecorateFiles` helper in the box store to reduce code duplication.