Exercise 1: A Sunday 02:30 Timer With Missed-Run Catch-Up — Possible Solution
====================================================================

[Unit]
Description=Run weekly-task.service every Sunday at 02:30

[Timer]
OnCalendar=Sun *-*-* 02:30:00
Persistent=true

[Install]
WantedBy=timers.target

Explanation:

This follows the chapter's own backup.timer structure exactly, with
values substituted for the exercise's own specific schedule. OnCalendar
=Sun *-*-* 02:30:00 combines the DayOfWeek portion of the chapter's own
syntax explanation (Sun for Sunday) with the explicit Year-Month-Day
wildcard and the specific 02:30:00 time, matching the general shape
"DayOfWeek Year-Month-Day Hour:Minute:Second" the chapter describes.
Persistent=true is included specifically because the exercise asks for
"missed-run catch-up enabled" -- exactly the setting the chapter names
as telling systemd to check at boot whether this scheduled trigger was
missed and, if so, run it once immediately rather than silently
skipping it. WantedBy=timers.target is included in [Install], matching
the chapter's own warn-box that this line is required for the timer to
be properly enabled via systemctl enable, rather than only working when
started manually.

WHY THIS WORKS AS AN ANSWER
------------------------------
This builds a complete, correctly structured .timer unit matching the
chapter's own established fields and syntax, with the specific day/time
and Persistent=true requirement from the exercise correctly
incorporated, including the required WantedBy=timers.target line the
chapter's own warn-box flags as easy to forget.