docs(ops): add controlled auto-update schedules

[typelicious]

What changed

• adds reviewed systemd service/timer examples for controlled auto-update schedules
• adds a cron example for hosts that do not use systemd timers
• updates README, onboarding, publishing, and releases docs with the conservative scheduling path

Why

• gives operators copy-pasteable scheduling examples without turning auto-update into default behavior
• keeps the update path explicit, helper-driven, and clearly separated from release publishing

How verified

• /usr/bin/git diff --check
• reviewed examples and docs against the current helper behavior
• branch contains docs-only changes