<!-- Add the related story/sub-task/bug number, like Resolves#123, or
remove if NA -->
**Related issue:** Resolves#37651
Switched to issue the SCEP fleet challenge on demand instead of ahead of
time.
# Checklist for submitter
- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
## Testing
- [x] Added/updated automated tests
- [x] QA'd all new/changed functionality manually
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Resolved Android certificate enrollment failures caused by SCEP
challenge expiration during offline periods, improving enrollment
reliability when devices lack connectivity.
* **Improvements**
* Certificate challenges are now generated on-demand when requested by
devices, rather than pre-generated, enhancing offline enrollment
support.
<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Victor Lyuboslavsky