feat: implement log-rotation for local sqlite storage

service_monitor.go

@@ -202,6 +202,9 @@ func (jep *JournalEntryParser) extractSystemdFields(journalData map[string]any,
 	for _, field := range systemdFields {
 		if value, ok := journalData[field]; ok {
 			esFieldName := strings.ToLower(strings.TrimPrefix(field, "_"))
+			if entry.Fields == nil {
+				entry.Fields = make(map[string]any)
+			}
 			entry.Fields[esFieldName] = value
 		}
 	}