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())

src/main.rs

@@ -120,22 +120,11 @@ fn activate_without_lock(
 }
 
 fn setup_logging() {
-    let mut builder = env_logger::Builder::from_default_env();
-    builder.filter_level(log::LevelFilter::Info);
-
-    let log_dir = PathBuf::from("/var/cache/moonlock");
-    if log_dir.is_dir() {
-        let log_file = log_dir.join("moonlock.log");
-        if let Ok(file) = std::fs::OpenOptions::new()
-            .create(true)
-            .append(true)
-            .open(&log_file)
-        {
-            builder.target(env_logger::Target::Pipe(Box::new(file)));
-        }
-    }
-
-    builder.init();
+    systemd_journal_logger::JournalLog::new()
+        .unwrap()
+        .install()
+        .unwrap();
+    log::set_max_level(log::LevelFilter::Info);
 }
 
 fn install_panic_hook() {