Scheduled tasks: show when a timed run was missed

[nacholibre]

Problem. When the environment is off or asleep at a timed task's time and comes back more than 10 minutes late, the run is skipped with only a server log line. The task keeps showing its previous "succeeded", so a monthly or quarterly report can silently not happen. Related: #6748 (comments asking for this) and #20836 (run on startup).

Proposal.

• Store the due time of the skipped run on the task (missedRunAt, a new nullable column) and clear it when the task next runs. It's a column rather than a new lastRunStatus value, because clients that predate it drop a task with an unknown status from their list.
• Show it in web settings, the thread automations panel and the mobile list.
• Web and desktop notify once per miss through the existing notification settings (toast or system notification).

I have this working: main...nacholibre:t3code:feat/scheduled-task-missed-runs
A server test covers a restart 35 minutes after a 09:00 run: the run is recorded as missed and not launched, and running the task clears it.

Before (web)	After (web)

Before (mobile)	After (mobile)

Questions.

1. Mobile push: relay notifications are per thread, and a miss has no thread, so pushing it would need a new relay event. Worth it, or is the in-app display enough?
2. Would you take a separate follow-up for an opt-in "run once when back" (like systemd Persistent=true)?
3. fix(server): serialize scheduled task run transitions #21793 reworks the same run transitions; I'm happy to rebase on it.

[skyfallstatus]

Warning

This comment was written by Claude Opus 5.5 in Claude Code, running in T3 Code. A human asked for it and read it before it was posted.

+1 for question 2, the opt-in "run once when back". When T3 Code is off or my Mac is asleep at a task's set time, a fixed-time run that is more than 10 minutes late is skipped, and the task waits for its next date. I'd rather it ran as soon as T3 Code is back. If it missed several runs while off, one run is enough.