feat(boxstore): add configurable expiry for one-time downloads

Introduces a new configuration setting `one_time_download_expiry_seconds` to allow administrators to define a default expiration period for one-time downloads.

The retention logic in `boxstore` has been updated to use this global expiry value when a box is marked as a one-time download and no specific retention period is defined in the manifest.

templates/box.html

@@ -29,7 +29,7 @@
                     <button class="box-address" type="button" id="box-address" data-copy-url="{{ .BoxID }}" title="Copy current page URL">{{ .BoxID }}</button>
                     <a class="win98-button box-toolbar-button" href="/"><img src="/static/img/icons/directory_open_cool-4.png" alt="" aria-hidden="true"><span>Upload</span></a>
                     {{ if .DownloadAll }}
-                        <a class="win98-button box-toolbar-button" href="{{ .DownloadAll }}"><img src="/static/img/icons/Windows Icons - PNG/zipfldr.dll_14_101-0.png" alt="" aria-hidden="true"><span>Download Zip</span></a>
+                        <a class="win98-button box-toolbar-button {{ if or .ZipOnly (gt (len .Files) 1) }}start-upload-cta is-current-step{{ end }}" href="{{ .DownloadAll }}"><img src="/static/img/icons/Windows Icons - PNG/zipfldr.dll_14_101-0.png" alt="" aria-hidden="true"><span>Download Zip</span></a>
                     {{ end }}
                 </div>