Current automatic update scheduling needs improvement

Describe your suggested feature

Currently, the automated update will always run at midnight UTC and noon UTC (when configured for 12 hours), or midnight UTC (when configured for 24 hrs).

It is impossible to get a schedule of say 5am/5pm UTC instead.

This is an issue for:

1. The user - as he cannot set automatic updates to run at a time that people are not using the internet (i.e. 3am).
2. The broader public - as all installations will try updating at the same time (midnight UTC), it hammers the sources servers.

The issue arises from: https://github.com/Suwayomi/Suwayomi-Server/blob/ec870759cfd252b08abee21d82a563457e748146/server/src/main/kotlin/suwayomi/tachidesk/manga/impl/update/Updater.kt#L153

where the "first" run is 0, which is midnight UTC. If we can control this value via docker parameter, command line, configuration, etc... some method, we can make it suitable for our own timezones.

This will:

1. The user - place burden on inactivity times, hence not affecting household members.
2. The broader public - stagger updates across the user base, as more likely than not, times suitable for different users is likely to be different. Hence, peak loads on source servers will lessen (and result in less 5xx responses from those servers during automated updates).

Other details

Although it was previously raised as a bug, the core information was not understood. https://github.com/Suwayomi/Suwayomi-Server/issues/1409#issuecomment-2910860693

This was subsequently clarified in discord, and the person told me to raise a feature request instead of bug report.

Acknowledgements

• I have searched the existing issues and this is a new ticket, NOT a duplicate or related to another open or closed issue.
• I have written a short but informative title (ideally less than ~100 characters).
• I have updated to the latest version.
• I have filled out all of the requested information in this form, including specific version numbers.