fix: improve exception handling and logging consistency

Replace stack trace printing with proper exception handling.

src/main/java/com/dgkncgty/logback/SystemdJournalAppender.java

@@ -174,7 +174,7 @@ protected void append(ILoggingEvent event) {
 
             journald.sd_journal_send("MESSAGE=%s", messages.toArray());
         } catch (Exception e) {
-            e.printStackTrace();
+            addError("Failed to append event to systemd journal", e);
         }
     }