feat: switch logging to systemd journal (v0.4.2)

Replace env_logger + /var/cache/moonlock file logging with
systemd-journal-logger. Logs are now reliably accessible via
journalctl --user -u moonlock, fixing invisible errors in the
systemd user service context.

- Cargo.toml: env_logger → systemd-journal-logger 2.2
- main.rs: setup_logging() uses JournalLog
- PKGBUILD: add systemd-libs dependency
- power.rs: include unstaged systemctl fixes (ABOUTME, --no-ask-password, output())

pkg/PKGBUILD

@@ -4,7 +4,7 @@
 # Maintainer: Dominik Kressler
 
 pkgname=moonlock-git
-pkgver=0.4.0.r0.g0000000
+pkgver=0.4.1.r1.g78bcf90
 pkgrel=1
 pkgdesc="A secure Wayland lockscreen with GTK4, PAM and fingerprint support"
 arch=('x86_64')
@@ -15,6 +15,7 @@ depends=(
     'gtk4-layer-shell'
     'gtk-session-lock'
     'pam'
+    'systemd-libs'
 )
 makedepends=(
     'git'