feat: add base systemd timers

These systemd timers are used to run the backup and prune services on a daily and weekly basis respecfully.
They are intended to be used for all hosts to keep them all on the same schedule.

roles/backup/files/restic-backup.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Run Restic Daily Backup
+
+[Timer]
+OnCalendar=*-*-* 03:00:00
+RandomizedDelaySec=15min
+Persistent=true
+
+[Install]
+WantedBy=timers.target

roles/backup/files/restic-prune.timer

@@ -0,0 +1,10 @@
+[Unit]
+Description=Run Restic Weekly Prune
+
+[Timer]
+OnCalendar=Sun *-*-* 04:00:00
+RandomizedDelaySec=30min
+Persistent=true
+
+[Install]
+WantedBy=timers.target