systemd does not perform shell-style tilde expansion, so a host path
starting with `~/` left in a generated Quadlet file is passed to Podman
as an invalid relative path and the service fails to start. Replace the
leading `~` with the systemd `%h` specifier instead.
Also fix the systemd specifier check in `absolute_clean_path()`, which
used `Path::starts_with()` and therefore only matched a path whose first
component was exactly `%`, causing `--absolute-host-paths` to prepend the
resolve directory to paths such as `%h/data`.
Closes: #166
Signed-off-by: DualFroz <me@dualfroz.com>