Programatic maintenance windows

[BigLep]

Done Criteria

There is a programatic ability for SPs to specify their maintenance window meaning they can set a time per day for 20 minutes where dealbot won't run checks against them.

This should get set in some place publicly accessible like the SP registry. (Public endpoint is also a possibility.)

https://github.com/FilOzone/dealbot/blob/main/docs/checks/production-configuration-and-approval-methodology.md#sp-maintenance-window should be updated.

Why Important

SPs need an opportunity to do maintenance.
Our existing daily time concentrates when SPs are doing mentnance which means we're more likely to have no SPs operating during this time

Notes

1. This builds on Routinely pause dealbot to allow for SP maintenance #163
2. There was https://linear.app/filoz/issue/XFN-197/mainenance-window-for-sps-to-indicate-they-do-not-want-to-receive about this in the past

[BigLep]

This most recently came up in 2026-04-08 colo discussion about SP telemetry and reliability. It was suggested to be M4.2 scope, but I pushed back 2026-04-09 during colo saying we should do this as a fast-follow (M4.5). For GA, we can just make sure that the 3 endorsed SPs choose different times to do their maintenance (e.g., :05, :10, :15 after the hour) since Curio updates/restarts are quick. We didn't have product management presence for this discussion, but @TippyFlitsUK was in alignment with this short-cut for now. (I surfaced this in slack as well, but unless we get directed otherwise, I have moved this to M4.5.)