Add a daily dump of the Library database

library-dump.timer writes Library-<weekday>.sql.gz to
~/.local/share/library_manager/dumps, which simple_backup then copies;
the login comes from ~/.config/library_manager/dump.cnf (not tracked).

.config/systemd/user/library-dump.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Dump the Library database to ~/.local/share/library_manager/dumps
+StartLimitIntervalSec=2h
+StartLimitBurst=4
+
+[Service]
+Type=oneshot
+ExecStart=%h/.local/bin/library-dump
+# MariaDB not up yet (e.g. caught up right after boot)? retry a few times
+Restart=on-failure
+RestartSec=5min

.config/systemd/user/library-dump.timer

@@ -0,0 +1,9 @@
+[Unit]
+Description=Dump the Library database daily
+
+[Timer]
+OnCalendar=daily
+Persistent=true
+
+[Install]
+WantedBy=timers.target