Excludes snap-generated mount files (`*snap*.mount`) and `snapd.mounts.target.wants`
from the `/etc/systemd/system` rsync backup task.
Prevents 'Invalid argument (22)' errors caused by escaped backslashes (`\x2d`)
in dynamic snap mount file names when syncing to non-POSIX destination filesystems.
Add the -L (--copy-links) flag to rsync calls for systemd units and cron
directories to dereference symlinks into actual target files, resolving
"Operation not permitted" failures on non-POSIX target filesystems.